FETools::get_fe_from_name() implemented for nonzero codimension

In addition to the new functionality, the internal structures mapping names to finite element factories have been improved, thus avoiding several specializations of functions.

This pull request fixes #86 (issue)
There is nothing you can specialize here since there is no function argument that depends on the template argument. But also: no, not allowed. C++03 didn't update the language spec beyond touching things that were actually broken.