this closes #17

to avoid them gettin gheader-checked on their own

- adds ability to compare matrices (leftover from dune-stuff)
- top-level compare/test functions are (manually) generated from
a python script instead of C macros

or ctest execution. This broke filtering tests
with ctest -R MASK

with 3.8 we were seeing kinda weird constructs, i.e. in for loops

which apparaently supersedes AlwaysBreakAfterDefinitionReturnType

also add check and recheck targets that
run DTX_TEST_PROCS many tests in parallel
and re-run only failed tests accord.

see http://clang.llvm.org/extra/clang-tidy/