- Add new setter and getter to the ICompilationUnit to configure
custom formatting options
- Save the custom options just in memory but not persist them in
the preference store
- Adopt the new API to fetch the formatting options from the
ICompilationUnit when rewriting AST

Change-Id: I1ecf9d7c673bb452b4e135fdbad29010c7f0b44e
Signed-off-by: Jinbo Wang <jinbwan@microsoft.com>