Multilang: gpi_vpi partially converted and compiling
MixedLang:  Push more up to the GPI layer
Changed interface to pass handles all the way up
MixedLang: Updated the API and everything else
Mixedlang: Add gpi_get_handle_by_index
Mixedlang: Functionality tests pass
Mixedlang: Add virtual destructores to fix mem leak
Mixedlang: Fixup sim Makefiles to use new lib names
Issue#161: Add new callback handle implemention file
Issue#161: Fix over zelous rename of libs
Issue#161: Move VPI_<state> to GPI level
Issue#161: Update GPI headers and common code - not working state
Issue#161: Update some pointers to const for functions and data that is callback related
Issue#161: Rest of const additions
Issue#161: Rename CPP files, split into headers and implementations, rename classes
Issue#161: To not initialise python twice
Issue#161: Update makefile file deps
Issue#161: Add vpiUnknown
Issue#161: Basis for checking if a requested handle is native to an implementation
Issue#161: Do not derive VpiCbHdl from VpiObjHdl