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: eda3d06fcef731589ace1b284159cead3416df9b@2637 af82e41b-90c4-0310-8c96-b1721e28e2e2

walty8/trac,netjunki/trac-Pygit2,walty8/trac,jun66j5/trac-ja,jun66j5/trac-ja,walty8/trac,netjunki/trac-Pygit2,jun66j5/trac-ja,walty8/trac,jun66j5/trac-ja,netjunki/trac-Pygit2