added a new formatter for CF(Mutable)BitVector

fixed a few potential NULL-pointer derefs in ValueObject
we have a way to provide docstrings for properties we add to the SWIG layer - a few of these properties have a docstring already, more will come in future commits
added a new bunch of properties to SBData to make it more natural and Python-like to access the data they contain

llvm-svn: 151962