P3Steel - Prusa i3 3mm Steel Laser cut based on v2.5

This is a remix of 2.5 frame version.

Changes to original design:

- changed top hole to 22m for Z axis bearing
- added 4mm holes in bed for SMAs
- added holes in frame for power supply and rambo housing

X-Ends are designed for threaded nuts.

20160519: Some progress done, but still few work need to be done ...
20160527: First print done