Move strip_attributes out of vendor/plugins
Move has_tag_string out of vendor/plugins
Move acts_as_xapian out of vendor/plugins

This includes making making sure that xapiandbs directory is moved
with this version of the code.
Move the acts_as_xapian generator into lib/generators
Update the acts_as_xapian generator to work under Rails 3
Move themes from vendor/plugins to lib/themes

These are essentially required in exactly the same way as before, but
from lib/themes rather than vendor/plugins.  This is the simplest
possible change in order make the themes work outside vendor/plugins,
I think, but it's not necessarily ideal.  It would be worth considering
whether these should be changed to Rails engines, as described here:

  http://guides.rubyonrails.org/engines.html
Revert "Silence deprecation warnings."

This reverts commit 084cc9574c254cc0af2de4cd615fa99a5be8bc83.
Merge branch 'move-plugins-out-of-vendor-plugins' into rails-3-develop