Differentiate build and install directories for static and shared libs

[kirichoi]

Furthermore, simplify cmake to have only SBOL_BUILD_SHARED option (False by default) and build static lib by default. Python wrappers should only use static lib to build library.

[kirichoi]

Commit 8b36bcd fixes the issue.

@bbartley : Please test it in Mac OSX for both static and shared libs. Also test building Python wrappers.