Forgot to move that one.

Signed-off-by: Felix Schindler <felix.schindler@wwu.de>

Paragraph 12.8/15 of the C++11 Standard:

The implicitly-defined copy/move constructor for a non-union class X
performs a memberwise copy/move of its bases and members

There is finally only one FunctionProvider, all specializations are gone.
The price for this is one additional line in all functions that should be
provided which is acceptable. See the added documentation of
FunctionProvider on how to proceed for new functions. The only drawback is
that there are still four places in functions.hh that need to be touched.
This is left as an exercise for someone who fancies static loops over tuple
types (not a tuple object), I am too tired now... :)

refs #282

refs #282

And implemented the current variant as a specialization. This allows us to
add a 2nd variant taking a diffusion factor and a diffusion tensor.

* change signature to common < E, D, d, R, r, rC > scheme and fail for
  wrong variants
* add default_config() and create() to Testcase1Force and
  Testcase1ExactSolution
* some white space

* added ESV2007::Testcase1Force
* added ESV2007::Testcase1ExactSolution
* renamed ESV2007Cutoff -> ESV2007::Cutoff

-rename namespace Function to Functions
-rename class Functions to FunctionsProvider