Add tests for ProcessEvents and ProcessEventsWithTriggerOffset

Test data currently not included because it is to big,
Run the script in the README.md to get the PE-testdata.h5
I’ll try to create a smaller data sample that can be included (less
traces?)
Fix ProcessEventsWithLINT

This should fix ProcessEventsWithLINT
when i == 0: x0 would get the last element, which could be anything
that made y0 >= y1 possible, possible divide by zero, etc..
this is now prevented.
Add tests for other ProcessEvents subclasses

Remove unused imports
The test ProcessIndexedEventsTests.test_process_traces works,
however, it causes progressbar output, redirecting stdout doesn’t work,
so for now it is disabled.