U1 Beam Examples and documentation

There is a userbeam.inp file in test examples package. When it comes to orientation of this element, there were 2 bugs related to it:

The second one is fixed but the first one still persists in the current version of CalculiX. It should be fixed in the next version though.

U1 element is meant to be used when beam has to be defined with section other than a few predefined ones.