Improve handling of configuration file and their invalidity

[tornede]

• PyExperimenter version: 1.3.0
• Database provider: -
• Python version: -
• Operating System: -

Description

In case the configuration file is invalid, only a single statement informing about it is returned to the user. It would be preferable to return concrete information WHY the configuration does not fulfill the requirements.

• Within the check, already log the actual problem of the configuration file
• Raise exception afterwards, as already done.
• Catch exception and also shown the original, abstract information to the user referring to the logging statement above, as already done.

[tornede]

This issue is related to issues #140 and #89

[LukasFehring]

This issue is done.