Timing and other related bugs

[fedem-p]

So after a lot of exploration I've found and pin pointed some of the timing/update problems related to planar mode, no trigger mode, etc...

List of Problems:

1. In volumetric mode and with the trigger not selected, if you try to change the speed of acquisition (volume frequency) the value isn't updated until you also change the duration of the experiment.

2. In planar mode, the value for the speed is not correctly updated. It will be fixed to the default no matter what you change.

3. No matter what duration you set in planar mode, it will acquire all the planes very quickly (as if it was trying to go as fast as possible instead of getting n_planes x second)

I'll try to work out these bugs in single PRs

[diegoasua]

Number 3 is a known issue. We never really finished the implementation of planar mode, particularly we were divided in how to trigger the plane scanning or whether it should try to acquire as fast as possible. Trigger gives you control, as fast as possible speed. But then you have to rely on the timer of the camera being accurate. See #2
Number 1 might be related to #21.