Port extractor to TBB
Replace omp atomic with std variant
Port StaticRTree to use TBB
Port Contractor to TBB
Set number of threads in TBB
Use append operator instead of function, because function is inplace.
Set requested threads in TBB
Add TBB to travis.ymk
Make some temporary variables const
fixes #1032:

- remove left-overs from OpenMP
- replace omp_* calls with TBB equivalents
replace a couple of std::sort calls with tbb::parallel_sort
test showing bug related to via points. see #1034
update test related to via points and #1034
fix test related to via points and #1034