Cleanup: Ensure that save_version_function is actually a function

This also improves readability.
Cleanup: Import just what we need
Cleanup: Fix import order
Cleanup: It is not necessary to check for build absence

It is always passed.
Cleanup: Use the right prefixes to avoid checks
Cleanup: Avoid unnecessary conversions
Cleanup: Move import to top of the function
Cleanup: Import just what we need
Cleanup: Rename constants to improve readability
Cleanup: Just save the build versions

There is no need to check for keys existence because we are initializing a
blank database.
Cleanup: Move code to separate function on initdb
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.
Partial pick of Evernote's evernote/pootle@2f453d22

Pick note: These changes might be required by the following picks.

    The rest of the changes in that commit are either necessary or where
    later dropped or changed at Evernote.
Make #footer stick to bottom

Conflicts:
	pootle/templates/layout.html
URL cleanups in Evernote dropped code

Change last URL template tags using references to views to instead use URL
names.
Make #footer stick to bottom
Fix footer overlapping with the content on tall pages

Conflicts:
	pootle/static/css/style.css
Partial pick: Added 'Terms and Conditions' links to the footer

Pick note: Only picked the CSS styles.

Conflicts:
	pootle/templates/layout.html