Revert the Codec Kit.

All of Barrett's individual reverts have been squashed into this
one commit, save a few actual bugfixes.

Change-Id: Ib0a7d0a841d3ac40b1fca7372c58b7f9229bd1f0

Beginnings of Encoder[Plugin] and Writer[Plugin] base classes and add-on
management.


git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@31922 a95241bf-73f2-0310-859d-f6bbb57e9c96