Allow relative timestamps and durations

[amotl]

Hi there,

in order to implement something along the line of InfluxDB duration types at all places where the operator can specify datetimes, dateranges, intervals or durations, like suggested at [1,2], this patch brings in a large refactoring of the sequencing machinery.

With kind regards, Andreas.

[1] https://community.hiveeyes.org/t/improving-time-range-control-for-grafanimate/1783/11 [2] https://community.hiveeyes.org/t/improving-time-range-control-for-grafanimate/1783/13

Features

• Allow relative timestamps / time ranges for start, stop and every parameters.

Plumbing

• Large refactoring. All utility functions related to times and time ranges are now located in the timeutil.py and model.py files.
• Add new model AnimationFrame
• Fix frame file sort order: Add index to each filename in order to reflect the position of the AnimationSequence in a list of many.
• Add --dry-run parameter
• Add a few more software tests
• Add CI configuration for GHA

/cc @msweef