Remove several unused commands and some other minor cleaning up
This merge requests removes several commands that are no longer of interest, mostly related to the online documentation system and time measurement.
In addition some smaller cleanups:
- The unused
low/ugmemory.h
header was removed. - Checks for standard C functions have been removed from
CMakeLists.txt
- The
bin/ugdemo
script was removed. It need demo applications that are not included in dune-uggrid.