Double precision support

[Andres Traks]

TODO:
Create a separate branch where btScalars are double instead of float in the managed assembly.

[Andres Traks]

Initial code: https://github.com/AndresTraks/BulletSharpPInvoke/tree/double-precision

[zorkind]

Is this branch updated i really need to use Doubles :(

[Andres Traks]

I merged the master branch to the double-precision branch.
There weren't too many significant changes.

[zorkind]

Good deal Andres, i was finally able to make it work, i think it was just me being dumb.

:)