Merge branch 'issue/documentation' into 'develop'

added documentation of DOFVector and DOFMatrix and improved the documentation of some other classes

See merge request !85
4 jobs for develop in 33 minutes and 58 seconds (queued for 3 minutes and 2 seconds)
Status Job ID Name Coverage
  Test
passed #8549
debian:10 clang-6-libcpp-17

00:30:39

passed #8548
debian:10 gcc-8-17

00:21:17

passed #8550
debian:9 gcc-6-14

00:22:17

passed #8551
ubuntu:18.04 clang-6-17

00:27:35