[MOV] content/*: move resource files into their related page's directory

Since odoo/documentation#903, the guideline for the location of new
resource (images, downloadable files, RST includes...) files is to place
those inside the directory of the RST page that references them.

For example, if `doc1.rst` has a reference to `image.png` and to
`download.zip`, the file structure should look like this:

├── parent_doc/
│     └── doc1/
│     │     └── image.png
│     │     └── download.zip
│     └── doc1.rst
│     └── doc2.rst
├── parent_doc.rst

Before this commit, most of the resource files were still located inside
'media' directories holding all the resource files referenced by RST
pages located at the same level as these directories. In the example
above, a single 'media' directory would hold all the resource files
referenced by both `doc1.rst` and `doc2.rst`. Doing so prevented us from
figuring out easily which resource file was referenced by which RST page
and, thus, lead to unused resource files piling up in the repository. It
also made it more complicated to define codeowners regex rules because a
team could not simply be assigned to `/some_page.*` but needed to be
assigned to both `/some_page\.rst` and to the location of 'media'.

In order to help new content writers figure out the guideline when
taking examples from other RST pages, this commit retroactively applies
the guideline to existing resource files and 'media' directories. The
left-over resource files that are not referenced by any RST page are
removed.

task-2497965

Part-of: odoo/documentation#2068

content/applications/finance/accounting/payables/pay/multiple.rst

@@ -16,13 +16,13 @@ In the following example, we will generate some bills. You can control
 the whole process from your accounting dashboard (first screen you get
 when you open the accounting application).
 
-.. image:: ./media/multiple01.png
+.. image:: multiple/multiple01.png
   :align: center
 
 To create a bill, open the Dashboard menu and click on **Vendor Bills**.
 In the Vendor Bills window, click on **Create**.
 
-.. image:: ./media/multiple02.png
+.. image:: multiple/multiple02.png
   :align: center
 
 Choose the vendor from which you wish to purchase the product, and click
@@ -32,14 +32,14 @@ on Add an item to add one (or more) product(s). Click on **Save** and then
 Pay supplier bills, one after the other
 ---------------------------------------
 
-.. image:: ./media/multiple03.png
+.. image:: multiple/multiple03.png
   :align: center
 
 We will now record a payment for one bill only. Open the bill, then
 click on **Register Payment**. Insert the Payment Method, Date and Amount,
 and click on **Validate**.
 
-.. image:: ./media/multiple04.png
+.. image:: multiple/multiple04.png
   :align: center
 
 Once you have validated the payment, the system will automatically
@@ -54,14 +54,14 @@ In order to illustrate the process thoroughly, create at least 2 more
 bills following the above standing guide. **Make sure all bills come
 from the same vendor.**
 
-.. image:: ./media/multiple05.png
+.. image:: multiple/multiple05.png
   :align: center
 
 In the Vendors Bills, select the new bills you have just created by
 checking the box next to each of them. In the Action menu located in the
 middle of the page, click on **Register Payment**.
 
-.. image:: ./media/multiple06.png
+.. image:: multiple/multiple06.png
   :align: center
 
 Insert the details of the payment. The system calculated the total
@@ -78,7 +78,7 @@ First, we need to create a payment
 This will handle from :menuselection:`Dashboard --> Bank journal -->
 More Option --> Send Money`
 
-.. image:: ./media/multiple07.png
+.. image:: multiple/multiple07.png
   :align: center
 
 Creating payment order with check payment method. Selecting related
@@ -86,7 +86,7 @@ Vendor and amount which remain to pay. After filling all details, we
 will confirm the payment order which will generate payment transaction
 with the system.
 
-.. image:: ./media/multiple08.png
+.. image:: multiple/multiple08.png
   :align: center
 
 As you can see, bill payment status show what is posted and what is
@@ -115,30 +115,30 @@ statements.
 We are adding payment terms which allow some cash discount where vendor
 offer us early payment discount.
 
-.. image:: ./media/multiple09.png
+.. image:: multiple/multiple09.png
   :align: center
 
 We are creating the following bills with the assignment of the above
 payment term.
 
-.. image:: ./media/multiple10.png
+.. image:: multiple/multiple10.png
   :align: center
 
 We have created the following bills:
 
-.. image:: ./media/multiple11.png
+.. image:: multiple/multiple11.png
   :align: center
 
 We will pay the invoices by creating bank statement where we will adjust
 the cash discount our vendor provided under payment terms.
 
-.. image:: ./media/multiple12.png
+.. image:: multiple/multiple12.png
   :align: center
 
 Before reconciling this bank statement, we need to create one statement
 model for cash discount.
 
-.. image:: ./media/multiple13.png
+.. image:: multiple/multiple13.png
   :align: center
 
 Now we are going back to bank statement and opening reconcile view.