Convert mwversionsinuse to pure python

Read versions from wikiversions.json file for parity with PHP codebase.
Also corrects a minor logic error in scap.scap where the wikiversions
data from common-local was being used instead of the prior behavior of
using the data from /a/common.

Support for the --home and --report command flags have been dropped from
the command line script. --home only makes sense on the deployment
prep server (tin) during a scap call and this behavior has been
accounted for internally in scap. The behavior of the --report flag can
be replicated by redirecting stderr to /dev/null when the script is
called.

Change-Id: I0db1c735370d06eee6378457ed001d82597fd72f