Adding new thrift commands for inspecting the graph

Summary:
Adding commands:
- --get-dirty-targets
- --get-inputs-of TARGET
- --get-outputs-of TARGET

This will be very useful for testing.

Test Plan:
Start the daemon and run falcon with the new commands. Example:
  $ falcon.py --get-outputs-of ../src/main.cpp
  ["CMakeFiles/falcon.dir/src/main.cpp.o"]

Reviewers: NicolasDP

Reviewed By: NicolasDP

Differential Revision: http://91.121.199.76/D40