[MOV] developer/reference: move up the standard_modules directory

With the renaming of the "Backend" and "Frontend" directories to "Python
framework" and "JavaScript framework", and since we may want to document
modules that mainly rely on JavaScript, it makes sense to move the
"Standard modules" one level up from under "Python framework" directly
under "Reference".

content/developer.rst

@@ -13,6 +13,7 @@ Learn through tutorials and get help using reference guides.
 
 .. toctree::
     :titlesonly:
+    :maxdepth: 3
 
     developer/howtos
     developer/reference

content/developer/reference.rst

@@ -9,3 +9,4 @@ Reference
 
     reference/backend
     reference/frontend
+    reference/standard_modules

content/developer/reference/backend.rst

@@ -17,4 +17,3 @@ Python framework
     backend/testing
     backend/http
     backend/mixins
-    backend/standard_modules

redirects/saas-15.2.txt

@@ -0,0 +1,12 @@
+# developer/reference
+
+developer/reference/backend/standard_modules.rst developer/reference/standard_modules.rst                                                                  # move standard_modules/ one level up (#2456)
+developer/reference/backend/standard_modules/account.rst developer/reference/standard_modules/account.rst                                                  # move standard_modules/ one level up (#2456)
+developer/reference/backend/standard_modules/account/account_account.rst developer/reference/standard_modules/account/account_account.rst                  # move standard_modules/ one level up (#2456)
+developer/reference/backend/standard_modules/account/account_account_tag.rst developer/reference/standard_modules/account/account_account_tag.rst          # move standard_modules/ one level up (#2456)
+developer/reference/backend/standard_modules/account/account_chart_template.rst developer/reference/standard_modules/account/account_chart_template.rst    # move standard_modules/ one level up (#2456)
+developer/reference/backend/standard_modules/account/account_fiscal_position.rst developer/reference/standard_modules/account/account_fiscal_position.rst  # move standard_modules/ one level up (#2456)
+developer/reference/backend/standard_modules/account/account_group.rst developer/reference/standard_modules/account/account_group.rst                      # move standard_modules/ one level up (#2456)
+developer/reference/backend/standard_modules/account/account_tax.rst developer/reference/standard_modules/account/account_tax.rst                          # move standard_modules/ one level up (#2456)
+developer/reference/backend/standard_modules/account/account_tax_repartition.rst developer/reference/standard_modules/account/account_tax_repartition.rst  # move standard_modules/ one level up (#2456)
+developer/reference/backend/standard_modules/account/account_tax_report_line.rst developer/reference/standard_modules/account/account_tax_report_line.rst  # move standard_modules/ one level up (#2456)