started implementing a transformer to generate the code for the initialization of `Mapper`s
Transformer is an AggregateTransformer now
collect all mappers in a class and create instances
needed more futures
only generate code in classes which inherit from `EntitySystem`
renamed SystemTransformer to DartemisTransformer because it'll transform more than just the systems (otherwise I'd have to parse the content several times to create the CompilationUnit, which isn't the fastest thing in the world)
create instances of Mappers in Managers
create instances of Managers in Systems and other Managers
System instances are assigned in Managers and other Systems
updated documentation, deprecated the mirror world, updated example to not use mirrors
analyze additional libraries if needed to build the class hierarchy
transformer knows every default EntitySystem and Manager, so dartemis doesn't need to be scanned/added as additionalLibrary
call super.initialize() if no initialize method existed prior to getting the instances for the fields
also fixed messing up the naming of rightHandSide and leftHandSide
minor changes/naming
Merge branch 'feature/transformers' into develop, fixes #32