Cleanup: Simplify code by merging functions
Cleanup: Remove intermediate function to save legacy build version
Cleanup: Remove unnecessary Meta from form

It appears to be used on djblets templates that are not used.
Cleanup: Buildversions are numbers, so default to zero
Partial pick: Drop dependency on Djblets’ SiteSettingsForm

We can do way with it by subclassing Django’s Form directly.

Pick notes: Partial pick of khaledhosny/pootle@1eb6c2bd. The rest of the
    changes don't apply since we dropped the ability to alter the settings
    from the home page in b4d46d65.

Conflicts:
	pootle/apps/pootle_app/views/admin/adminpages.py
	pootle/apps/pootle_app/views/index/index.py
Replace djblets: Add functions to retrieve site title and description

This avoids us retrieving all the site config in the place where we need the
title or the description.

Also helps exposing each separate use for siteconfig so it is easier to
replace.
Replace djblets: Move ability to save buildversion to pootle_misc

This avoids us retrieving all the site config in the place where we save the
build versions.

Also helps exposing each separate use for siteconfig so it is easier to
replace.
Replace djblets: Move code to retrieve buildversion to pootle_misc

This avoids us retrieving the build versions in the place where we need the
build versions.

Also helps exposing each separate use for siteconfig so it is easier to
replace.
Replace djblets: Add a new PootleConfig model to save the build versions
Replace djblets: Add PootleSite model to store the title and description
Replace djblets: Use a single function to get Pootle build, wherever it is
Cleanup: Save as POOTLE_BUILDVERSION instead of legacy BUILDVERSION

Since the previous commit the code works fine just using POOTLE_BUILDVERSION
instead of BUILDVERSION.

Note that this requires treating the build version as a string.
Replace djblets: Use a single function to get the Toolkit build
Replace djblets: Retrieve title and description using new PootleSite model