add data-version-added and -deprecated attributes.

These attributes replace the need for the "apilevel-N" class names.
But they'll both stay for now, until we fully migrate to the new
 script that reads the data attribute instead of the class names.
Also cleanup whitespace around the head tag's new django include
 and remove obsolete 'alt-color' style from the pre-CSS3 era
Bug: 67899891
Test: make ds-docs
 the result of which is (partially) visible in cl/177537941

Change-Id: Id3110304644cf126f3908d8766eb7c2e1d11f3d2
5 files changed