Add a mimetype plugin to organize AUs based on mimetype.

* Add a sample XML document for mimetypes.
* Add a comment field to AUs to describe where they came from.
* Remove some extraneous logging from PLNTitledbImportCommand#addAu
* Automatically load settings.yml files for plugins.
* Mangle the auids that are getting generated slightly.
Allow content mimetypes to match wildcard mimetypes (e.g. application/*) from settings.yml.

Requires a composer update.
Add tests to the AusByType plugin and fix some bugs.
more documentation.
New LOM Plugin: organize aus by title.
better plugin settings handling and display settings in the plugin manager (at least for now).
Test loadSettings() in abstractPlugin and fix a big.
Have AusByTypeTest use overridden settings for testing.
AUsByType now selects AUs for deposit based on groups of mimetypes, rather
than one mimetype for each AU.
fix a but that passes tests on my computer but not on Travis. Strange.
fix a but that passes tests on my computer but not on Travis. Strange. This is attempt number two.
Allow any bundle to have plugins, not just the PluginBundle. Because
that was a pretty silly limitation. We don't want admins to have to muck
about with our code (or they should muck with it as little as possible).
fix some namespace issues due to moving things around. Refactor and
document the event SWORD identifiers.
refactor the plugins and the plugin tests.
add tests for ausbytitle.
Merge pull request #20 from ubermichael/newplugins

Newplugins