Add energy calculations and improve build setup

* Initial commit of some energy calculations code

* Rearrange build setup
  i.e. more files built properly (with .cc and built into micromag lib)

** Requires lots of functions to be made "inline"

** Requires lots of Makefile.am s to have "-lmicromag"
Add energy calculations to llg problems, including output to trace file

along with dummy self test.

Make Dummy_doc_data protected so we can get at it in inheriting problems.

Problems with semi implicit problems: can't do energy calculations...
Enable energy calculations for semi implicit models

* Add local coordinate storage to interpolators

* Move magnetostatic field calculations to functions

* Move semi-implicit magnetostatic field calculation to get_magnetostatic_field
  (rather than just putting it into applied field, this allows energy
  calculations).