Add tool for helping with library graduation

This new script prepares a copy of the oslo-incubator repository
to house a stand-alone oslo library by revising the history,
retaining commits for files that are part of the new library and
discarding commits for files that are not. It then uses the
new oslo-cookiecutter library to inject any missing structural
files so the packaging and tests will work.

Change-Id: I1f513a773589f034975ae6ee54c5a418e4bfce25
Merge "Add tool for helping with library graduation"