Changing of output directory

* Changed output directory for binary from
  main directory to bin subdirectory
Adding of []-operator for matrices

* Implemented the possibility to overload
  the [] operator to access matrices directly.
Refactoring, rotation around pivot

* Refactored code a bit to create the spheres
  with a loop instead of each one apart
* Implemented rotation around pivot to be able
  to rotate the whole cube and the spheres with it