Improvements for make commit dialog

[NattyNarwhal]

• Change committer/author
  • Perhaps this can be set from the options for SCC too.
  • This will also likely need revision to the get committer dialog so it doesn't need to set the config options.
• Highlight things w/ commit messages (comments, recommended line size, gap between summary and body, cursor position, etc.)
  • This may involve using Scintilla or something with a customer lexer....
  • Could we shell out to an external editor?
• Show status (what things we're committing)
• If we can amend commits in the middle of history, we should be able to amend commit messages/signature from history.

[NattyNarwhal]

Minor work on the signature dialog to allow for changing the committer is done.