Save sequence configuration + tests.
Save interpolant configuration + tests.

The read_interpolant function was already present, having been committed previously by mistake. The tests resulted in a small fix making the parameter applicable also for the inv method
Merge branch 'ptvis_mem' into working_branch

Added 'traj_min_len' as a saved key with override.

Conflicts:
	flowtracks/sequence.py
Merge branch 'working_branch'

* working_branch:
  Save interpolant configuration + tests.
  Save sequence configuration + tests.