changed name of file AxisAlignedBoundingBox.h to AABB.h according to the style guid rule: class name equals file name

This reverts commit 05677165.

Conflicts:
	FileIO/XmlIO/XmlGspInterface.cpp
	README.md

renamed namespace GEOLIB to GeoLib in order to be consistent with other OGS-libraries and directory names

- FileFinder.h
- FileTools.h
- TimeMeasurementBase.h
- quicksort.h

changes due to namespace changes in:
- PointVec.cpp
- Polygon.cpp
- AdjMat.cpp
- CRSMatrixReordered.cpp

changed size_t to unsigned; included a few (yet unimplemented) methods for mesh-consistency checking

- added test programm for solving a linear system with CG-method
- time measurement is at the moment OS dependent!
- added Base folder
- added GeoLib folder
- added files in MathLib folder - restructured MathLib folder