Optional: Pipeline improvements

Petr suggests:

Example: https://gitlab.fi.muni.cz/xondusk/pa165-team-delta

The pipeline seems satisfactory, but I noticed that there is only one job in the stage. Having a separate job for each module would not only speed up the build and test time due to parallel jobs, but also make it easier to identify any failures. In case of a pipeline failure, having a separate job for each module would allow you to quickly identify which module is broken and needs to be fixed.