The Relationship between ImmutableCFOptions , MutableCFOptions, and ColumnFamilyOptions should be cleaned up

As the code is currently written, you can create ImmutableCFOptions and MutableCFOptions from a ColumnFamilyOptions but the inverse is not true. This limitation is at least partially true because the ImmutableCFOptions uses "raw pointers" in it instead of the "shared" pointer.

I think an ImmutableCFOptions may also contain some of the options from DBOptions, and that should probably also be cleaned up.