HFR History should only contain statistics from sequence exposures

[Stefan B]

In the case a user runs autofocus and platesolving during a sequence, the HFR history gets bloated into a state where it is not useful at all. Example:

Furthermore it should clear when a new sequence target starts.

Additionally a clear button to manually clear the list could prove useful.

[Stefan B]

Having a setting option, which stats should be displayed could be helpful, too.

E.g. adding Mean and StDev to the graph.

[Aaron McKlascky]

+1

[Calvin Musch]

Adding to the setting option, make an option to enable/disable clear on new sequence start. E.g. i sometimes like to see my history over multiple seqences.

[Stefan B]

Issue #170 was marked as a duplicate of this issue.