renamed DOFVectorConstView into DiscreteFunction and added some more interpolation methods

4 jobs for feature/dofvector_global_evaluation in 20 minutes and 37 seconds (queued for 5 seconds)
Status Name Job ID Coverage
  Test
passed debian:10 clang-6-libcpp-17 #6885

00:20:36

passed debian:10 gcc-8-17 #6884

00:15:14

passed debian:9 gcc-6-14 #6886

00:13:11

passed ubuntu:18.04 clang-6-17 #6887

00:19:15