Checkpointing test

[giadarol]

The test should clean-up existing checkpoints before starting
Possibly move checkpointing tests outside test buildup
Is timing really working?

[giadarol]

Timing looks a bit tight, probably we should lengthen a bit the simulation

[giadarol]

Check that no output is messed up (MP states, pol states, etc)

[giadarol]

I worked a bit on it for #108, much better now (mainly in the main output)

[giadarol]

t_hist seems to be cut up for some reason --> to be investigated

[giadarol]

The test should clean-up existing checkpoints before starting
Possibly move checkpointing tests outside test buildup
Is timing really working?

Sorted now