Fix bug in RF foil conversion from DetDesc
The alpha1 and alpha2 attributes of the Trap shape were incorrectly called alp1 and alp2 (as they were in DetDesc) throughout the RF foil description. As such, they were silently ignored!
This is a similar bug to that fixed in !46 (merged) in that it arises from a minor mismatch in tag names that is silently ignored.
Edited by Thomas Latham