Removed commented OGS-5 code form ProcessInfo.{cpp,h}.
Removed unnecessary include and forward declaration.
Using reference instead of full copy.
Adding include in the test instead of the xml interface impl. file.
Creating GEOObjects or GEOModels instance within class ProjectData.

As a consequence removed the method ProjectData::setGEOObjects().
Moved managing of ProjectData one level deeper in the inheritance hierarchy of XMLInterface.
Using GEOObjects instances directly instead of always fetching it from class ProjectData.
Changed sequence of arguments (output,input) -> (input,output).
Moving Qt dependencies out of XMLInterface to XMLQtInterface.
Moved XML implementations deploying Qt stuff into subfolder.
[XmlCndInterface] readFile() interface change!

- readFile() put the read data into instance of ProjectData instead of a vector.
- For the same reason readConditions() was changed.
- The data is not added via the ProcessModel::addCondition() anymore!
Removed useless const specifier for return value.
Use call by reference to omit a copy.
Merge pull request #242 from TomFischer/PreparationsForImplOf2dGWFExample

Preparations for implementation of 2d ground water flow example.