[MOV] documentation structure reorganization

This commit aims to improve the documentation's navigability by
redefining some categories' purposes and titles.

There is a redirection rule for each documentation page moved.
This ensures that users won't have a 404 error message.

task-3217827

content/applications/finance/accounting/customer_invoices.rst

@@ -47,7 +47,9 @@ Draft invoices
 --------------
 
 The system generates invoice which are initially set to the Draft state.
-While these invoices remain unvalidated, they have no accounting impact within the system.
+While these invoices
+
+remain unvalidated, they have no accounting impact within the system.
 There is nothing to stop users from creating their own draft invoices.
 
 Let's create a customer invoice with following information:

redirects/15.0.txt

@@ -16,7 +16,7 @@ administration/maintain/hosting_changes.rst administration/hosting.rst
 administration/maintain/mailjet_api.rst applications/general/email_communication/mailjet_api.rst              # administration/maintain/* -> applications/general/email_communication/*
 administration/maintain/odoo_online.rst administration/odoo_online.rst                                        # maintain/* -> *
 administration/maintain/on_premise.rst administration/install.rst                                             # maintain/on_premise -> install
-administration/maintain/supported_versions.rst administration/supported_versions.rst                          # maintain/* -> *
+administration/maintain/supported_versions.rst administration/maintain/supported_versions.rst                 # maintain/* -> *
 administration/maintain/update.rst administration/on_premise/update.rst                                       # maintain/* -> on_premise/*
 
 # applications/finance