This way, the pipeline result on master will always be the one of the 
last nightly scheduled pipeline.

the ci seems to sometimes fail to pass the created .yml file to the
subsequent stage. Thus, we now always run the test-selection stage but
skip script execution in case we are not in a merge request

The test selection script requires gcc to be used

[ci] manual trigger pipeline only when not scheduled

See merge request !2575

WIP Feature/ci integration

See merge request !2408

For a large number of tests, the resulting .yml could not be interpreted 
by the GitLab ci

use the generator script from the template instead

Changed parameters for linear solver to reduce iterations

Closes #950

See merge request !2570

Math: add a function for linear regression

See merge request !2569

[pnm] Various imrprovements

See merge request !2568

* function doesn't add any value
* use ctor of BasicParams directly