Add task to print transitive dependencies and their license files.

Print modules and their transitive dependencies with license files.
To invoke, run
"make deps-license PROJ_PATH=<proj-path-patterns> DEP_PATH=<dep-path-patterns>".
PROJ_PATH restricts the paths of the source modules;
DEP_PATH restricts the paths of the dependency modules.
Both can be makefile patterns supported by makefile function $(filter).
Example:
  $ make deps-license packages/app/% external/%
  prints all modules in packages/app/ with their dpendencies in external/.
The printout lines look like "<module_name> :: <module_paths> :: <license_files>".

Bug: 20823995
Change-Id: I06b66e85ff56c8628bffa3d948085ed45870100f