Add various happy/unhappy unit tests for both IPE's policy parser.

Besides, a test suite for IPE functionality is available at
https://github.com/microsoft/ipe/tree/test-suiteSigned-off-by: Deven Bowers <deven.desai@linux.microsoft.com>
Signed-off-by: Fan Wu <wufan@linux.microsoft.com>
Signed-off-by: Paul Moore <paul@paul-moore.com>