Add support to read include/exclude paths from file

Files containing the list of paths to be included and excluded can now be
specified through -include-from=<filename> and -exclude-from=<filename> command
line options in cpp11-migrate.

Added support for data files for cpp11-migrate unittests. The Cpp11MigrateTests
executable just requires a DATADIR environment variable to be set which
specifies the directory where data files are stored. This is handled
automatically when using LIT.

Author: Jack Yang <jack.yang@intel.com>, Edwin Vane <edwin.vane@intel.com>