[cmake] removes empty lib/CmakeLists.txt
[common] adds threading abstraction
[common] changes profiler to keep both user+sys and walltime
[common] fixup new profiler code
[profiler] hide internals
lessen type restriction on make_quadrature, else it fails w/ alugrid
[cmake] removes empty lib/CmakeLists.txt
Merge branch 'master' into threading

Conflicts:
	dune/stuff/common/profiler.cc