Refactor the way ticket timeline events are generated.
Refactor the way ticket timeline events are generated.

The `UpdateDetailsForTimeline` component is gone (sigh, my first plugin...)
and the change and update events are now generated by roughly the same code.

This closes #1895.


git-svn-id: 0d96b0c1a6983ccc08b3732614f4d6bfcf9cbb42@2637 af82e41b-90c4-0310-8c96-b1721e28e2e2

rbaumg/trac,rbaumg/trac,rbaumg/trac,rbaumg/trac