Reorganize File Structure

[bbatsche]

Clean up the src directory a bit:

+- src/
   +- Verifier/
   |  +- Base.php
   |  +- File.php
   |  +- Value.php
   |  +- Object/
   |  |  +- Property.php
   |  |  +- Method/
   |  |     +- ReturnValue.php
   |  |     +- ThrownException.php
   |  +- Data # Not this, need a better name here
   |     +- ArrayContent.php
   |     +- JsonContent.php
   |     +- FileContent.php # Maybe?!
   +- Support
   |  +- TestExecution.php 
   |  +- ExecutionInterface.php # Same
   |  +- ConstraintFactory.php
   +- Exception
      +- ...