Make some of the demos in HPC-GAP into tests.

[markuspf]

Most of the examples in the demos/ folder either don't work, or do not work in an obvious way.

Make some meaningful demos, and also use them as tests.

[olexandr-konovalov]

Agree. For the moment, demo/demo.g is known to work and what is used in regression tests with Jenkins CI - I suggest to run it if you make any changes and would like to test them.

[olexandr-konovalov]

@ChrisJefferson I suggest that I will create new directory tst/hpcgap and move tests from demo directory there, starting from those that we run as a part of HPC-GAP tests with Jenkins.