SL-49406: template_verifier.py requires network access to build.  Implemented a 4-hour cache so it hits the network less often overall (saving approx .5 seconds every build), and added fault tolerance for when it fails to fetch the master over the network.  It'll whine at you if it can't fetch it, but even if it can't get the master from the network and doesn't have a cached copy at all, it will still at least do a syntax check on the local template.

Replaced usage of urlopen.read(), which isn't guaranteed to return all of the downloaded bytes, with urlopen.readlines(), which (I believe) does have that guarantee.  This should fix the rash of mysteriously-failing prebuilds.  In the process, added some better error messaging about whether the local template has the parse error, or the master on the network.  Also some reorganization.  Reviewed by Tess and Leyla.

Result of svn merge -r65183:65337 svn+ssh://svn/svn/linden/branches/python-shuffle into release. Also includes untabification of many python files.

svn merge --ignore-ancestry svn+ssh://svn/svn/linden/release@65088 svn+ssh://svn/svn/linden/branches/release-candidate@65078 -> release Paired by Tess and rdw.