added Vector (2d,3d,4d) classes, Linear equation solver, Least squares optimizer

The purpose of these additions is to support more sophisticated arm solutions and kinematic models. The least squares optimizer will be very useful for calibrating such kinematic models and builds the foundation for more accurate arm solutions and less manual tuning of machine parameters.

- Added a math directory in 'src/libs/'
- included 2d,3d,4d vector classes for convenient vector calculations 
(vector classes originate from a another project and are well tested)
- added a lightweight linear equation system solver 
- added a lightweight least squares optimizer

An arm solution that features automatic model optimization and demonstrates the use of the above classes will soon be added as well.