Add in more commonly used utilities

[burz]

Describe your changes Added:

• FindFunctions to find the functions that are declared within source units.
• SourceUtil for commonly used source-related functionality not provided by LibTooling itself
• MatchForwarder to forward matches to function objects so that classes are not necessary each individual type of match.

Testing performed Added tests for FindFunctions.

@ruoso @dbeer1 @azeemba