NSTAR-2953 Modified SCons 2.3.1 to work with cygwin python
- use environment variables instead of registry VS120COMNTOOLS, VCINSTALLDIR
- allow caller to specify visual studio project builder script
- implemented custom visual studio project builder to use CL, LINK instead of SCons to build
- use cmd.exe instead of sh for executing scripts
- changed "except:" to "except Exception:" everywhere
- use utf-8 instead of mbcs encoding (cygwin python does not support mbcs)