Item2595: Item11301: Item11820: Item12287: Extender

These are probably all related to plugins having issues when either not
fully configured, or when the environment is not fully established.

Disabling all extensions during installation will hopefully resolve all
of these.

git-svn-id: http://svn.foswiki.org/trunk/core@17644 0b4bb1d4-4e5a-0410-9cc4-b2b747904278