[Insight-developers] fem registration filter test

[Brian]

Hello,

I checked in a FEM registration filter test.  I also made the necessary
changes to the algorithm headers and algorithm tests .cxx files as well as
cmakelists.  however, all the changes are commented because i was unsure
about how to handle the situation where FEM is not built.  If FEM is
always built, then the comments can be removed.

Let me know if anyone has any questions.

Brian