Update auto-generate-resources to show what resources were changed

This is in preparation for another resource-related CL.

Switched to lxml for xml parsing as it implements line numbers,
which has the consiquence of having to change the current.xml file to
2-space indentation, which is all libxml2 allows.

auto-generate-resources will no longer create a temp xml file when
in compare mode.

Test: Manually
Change-Id: Idc1f2f3faaadcd742c5480b1918044e3eada8773
5 files changed