Skeleton project data

This provides skeletons needed for process/solver class and a reworked `ProjectData` class.
All files from `OGS/` dir are distributed in the new `ProcessLib/` and `Applications/` directories and the `OgsLib` is also substituted with `ApplicationsLib`.
The new structures are used in the [GroundwaterFlow](https://github.com/endJunction/ogs/tree/GroundwaterFlow) and [CommandLineApplication](
https://github.com/endJunction/ogs/tree/CommandLineApplication] branches.

**For easier review please note:**
 - Most commits are just removing files.
 - Changes on files with one to three changed lines are adjustments of the includes or namespaces.
 - The interesting stuff consists of the new/moved files listed below.

Please take a look on (buttom-up order):
 - ProcessLib/BoundaryCondition
 - ProcessLib/InitialCondition
 - ProcessLib/ProcessVariable
 - ProcessLib/Process
 - ProcessLib/GroundwaterFlow
 - Applications/ProjectData
i see we have a different veiw about the variable. i considered it as a field of physical quantities (so it could be a vector field) while you take it as scalar unknowns in linear equation systems. This is something we need to discuss later. But at this stage, you can keep it as you think. `numberOfNodeComponents` sounds consistent with other classes.