Merge branch 'feature/update-and-clean-examples' into 'master'

examples/2pinfiltration/doc/main.md

examples/2pinfiltration/main.cc

examples/embedded_network_1d3d/solver.hh

examples/freeflowchannel/README.md

examples/freeflowchannel/main.cc

examples/liddrivencavity/doc/problem.md

examples/liddrivencavity/main.cc

examples/shallowwaterfriction/doc/main.md

examples/shallowwaterfriction/main.cc