[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/others/analytic/purchases_expenses.rst

@@ -20,17 +20,18 @@ Configuration
 The following modules needs to be installed to track cost. Enter the app
 module and install the following apps:
 
-+---------------------------------+---------------------------------+---------------------------------+
-| .. image:: media/purchase01.png | .. image:: media/purchase02.png | .. image:: media/purchase03.png |
-+=================================+=================================+=================================+
-+---------------------------------+---------------------------------+---------------------------------+
+.. list-table::
+
+   - - .. image:: purchases_expenses/purchase01.png
+     - .. image:: purchases_expenses/purchase02.png
+     - .. image:: purchases_expenses/purchase03.png
 
 Please note that the applications provided by these apps only allows us
 to **track** the costs. We won't be able to automatically re invoice
 those costs to our customers. To track and **re invoice costs** you
 should install the Sales management app as well.
 
-.. image:: media/purchase04.png
+.. image:: purchases_expenses/purchase04.png
    :align: center
 
 Enable Analytical accounting
@@ -40,13 +41,13 @@ Next step is to activate the analytical accounting. In the accounting
 app, select :menuselection:`Configuration --> Settings` and thick the Analytic
 accounting box.
 
-.. image:: media/purchase05.png
+.. image:: purchases_expenses/purchase05.png
    :align: center
 
 Moreover, scroll down and tick the **Analytic accounting for purchases**
 box.
 
-.. image:: media/purchase06.png
+.. image:: purchases_expenses/purchase06.png
    :align: center
 
 Don't forget to save your changes.
@@ -59,7 +60,7 @@ point all your expenses. Enter the accounting app, select
 :menuselection:`Configuration --> Analytic Accounts`. Create a new one. In this
 case we will call it "consulting pack" for our customer Smith&Co.
 
-.. image:: media/purchase07.png
+.. image:: purchases_expenses/purchase07.png
    :align: center
 
 We will point all our costs to this account to keep track of them.
@@ -79,7 +80,7 @@ Click on :menuselection:`Configuration --> Expense Products`. Create a new produ
 called Train ticket and set the cost price to 15.50 euros. Make sure the **Can be
 expensed** box is ticked.
 
-.. image:: media/purchase08.png
+.. image:: purchases_expenses/purchase08.png
    :align: center
 
 Book the expense
@@ -89,7 +90,7 @@ Enter the Expense module, click on :menuselection:`My expenses --> Create`. Sele
 Train ticket product and link it to the analytical account discussed
 above.
 
-.. image:: media/purchase09.png
+.. image:: purchases_expenses/purchase09.png
    :align: center
 
 Submit to manager and wait for the manager to approve and post the
@@ -107,7 +108,7 @@ Within the line we can link the product's cost with the analytical
 account. Specify the order line and select the correct analytical
 account. Confirm the sale.
 
-.. image:: media/purchase10.png
+.. image:: purchases_expenses/purchase10.png
    :align: center
 
 Accept the delivery and enter the invoice. Once the invoice is entered the cost
@@ -137,7 +138,7 @@ Enter the accounting module, click on :menuselection:`Advisers --> Analytic Acco
 Select "consulting pack - Smith" and click on the cost and revenue
 button to have an overview of all cost linked to the account.
 
-.. image:: media/purchase11.png
+.. image:: purchases_expenses/purchase11.png
    :align: center
 
 .. note::