Solver changes commited

I finished updating the constraint tests for the new solver and commited the changes. The current revision, which contains the solver changes and a few release fixes, is here.

Until all the constraints will be ported to the new structure, the old ones will remain and all the new classes will have an added 'Ref' to differentiate them from the old ones and the tests are only for the constraints that are currently implemented for the new solver:
- horizontal line
- vertical line
- parallel lines
- perpendicular lines
- point on point
- point on line

Aside from the constraints that I've showed here and here, the solver works on more complicated shapes:



Here we have three rectangles that have common corners. When one of the points is dragged, the constraints and related shapes lists are loaded - in this case, all the points are related to the point being dragged, but they are sorted according to their level and only the minimum number of points is changed.