[ADD] accounting: add new doc about fiscal localization packages (#649)

- move all files in accounting/localizations --> accounting/fiscal-localizations/localizations
- fixes paths after the moves defined above
- add new doc about fiscal localization packages
- add references to the new doc mentionned above in the following docs: initial setup, tax returns and chart of accounts

accounting/fiscal_localizations/localizations/netherlands.rst

@@ -0,0 +1,23 @@
+Netherlands
+===========
+
+XAF Export
+----------
+
+With the Dutch accounting localization installed, you will be able to
+export all your accounting entries in XAF format. For this, you have to
+go in :menuselection:`Accounting --> Reporting --> General Ledger`, you
+define the entries you want to export using the filters (period, journals, ...)
+and then you click on the button **EXPORT (XAF)**.
+
+Dutch Accounting Reports
+------------------------
+
+If you install the Dutch accounting localization, you will have access
+to some reports that are specific to the Netherlands such as :
+
+-  Profit & Loss
+
+-  Tax Report (Aangifte omzetbelasting)
+
+-  Intrastat Report (ICP)