Try to fix some failing tests on travis CI for Vector3 associated to default constructor of Vecor3.

Changed also
- the data type that holds the coordinates from pure C array to std::array<T, DIM>,
- the implementation of write() and read().

- Implemented class template GeoPoint (see GeoLib/Point.h) and substituted class templates in the typedef.
- Some changes due to changed namespace in MathLib/Vector3.h and GeoLib/Color.h.

This reverts commit 05677165.

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

- removed method write()

- added template classes Grid and OctTree for efficiently searching in point sets

removed

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

- renamed method to access coordinates from getData() to getCoords()

- 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