use readonly_files

[smoors]

• update CI/run_reframe.sh to use a shared file system
• raise error if readonly_files is an empty list
• add readonly_files to all tests
• remove staging fixtures from cp2k and lammps
• remove __init__.py from sourcesdirs add missing __init__.py files with added comment why they are there

fixes #211

[casparvl]

Please don't remove the empty init files, they are needed by the automatic API generation tools. Seems silly, but it is what it is :)

[casparvl]

Note: I haven't tested this PR yet, I'll do that once we agree on the actual changes in the code :)

[boegel]

Please don't remove the empty init files, they are needed by the automatic API generation tools. Seems silly, but it is what it is :)

Maybe we can put a comment in the init files to explain why they're there?

[smoors]

Note: I haven't tested this PR yet, I'll do that once we agree on the actual changes in the code :)

for reference: they were only removed from the src directories, but we agreed that it's useful to have a list of the sources in the docs too.
i'll add them back

[casparvl]

Code changes look good to me (barring the __init__ removals), now running

reframe --system=snellius:rome -t CI -t '1_nodes|2_nodes' --run

just to test.

Update: all tests passed.