StairBuilder v.1.0 beta2

* Stair builder-1.0 beta2 news:
-add a CHANGELOG.TXT
-fix the bug created by me on the cut out shape for round spiral stairs
-fix a bug in information label for tread width when other option than Square Spiral are selected
-have adjusted some translations accordingly with sjb007 & Keet's suggestions
-set the author name to "anonymous" until will be a dedicated text field for this.

TODO (or at least what I intend to do):
-to implement somehow a customizable cut-out-shape in respect of minim headroom requirement.
-to add somewhere a picture with the specific terms used on stairs.
I intend to change again the names accordingly to this.
Like:
-"Riser" in place of "Last step elevation"
-"Run" in place of "Tread depth"
-"Rise" in place of "Tread height"
-"Nosing" in place of "Tread offset" etc.
But I have to explain somehow to the users who know nothing about that terms.

@Keet Almost everything it is possible but not all are easy.
All components of this stair are generated by extrusion.
I don't have enough knowledge about 3D object manipulation so, you will have to wait until I will learn.