Merge branch 'feature/galerkin-threaded' into 'master'

Threading of GalerkinOperator.

See merge request !34

(cherry picked from commit fcb688d6)

98c72cdc [cleanup][ThreadHandle] Renamed to ThreadPool and moved to dune-fem.
0b78e431 [cleanup] remove duplicate parameters
8e9e5d0d [feature][Vortex] Added isentropic vortex case.
96a7e256 [bugfix][Passes] Rerun in single thread mode when SingleThreadModeError
b376b9c1 [cleanup][Euler] Enable limited operator by default and set sod as
ab59be73 Added OMP_NUM_THREAD to chem test.
5af6db1d [cleanup] Remove warnings and increase timeout.
e7e7edbb [feature][ThreadPass] allow to use flexible number of threads.
7a2e0733 add a 'default' for the threading parameter in the dg operator which turns...
92e68922 adapt code to moving threadmanager/pool to mpimanager - setting the max thread...
99db4d58 Set periodic bnd conditions in y-direction to avoid bnd errors.
dbe8af02 [bugfix][build-script] Enable shared libs by default.
d31cf80c [cleanup][ThreadPass] isMaster --> isMainThread.
de827914 [cleanup][Python] .grid --> .gridView
ebd1f6e6 Merge branch 'master' into feature/galerkin-threaded