Adding buttons to save/load/update settings

[seb5g]

The idea is to be able, for each ParameterTree to load/save its state into an xml file. It is particularly useful for settings from detectors or actuators but not only.

Branch settings is working in that direction

A global widget with a splitter splitting a toolbar and a regular ParameterTree is replacing the ParameterTree in the ParameterManager:

The splitter allows to hide the toolbar for compactness!

[seb5g]

The load button could actually be two buttons:

• a load : replacing the settings from the content of a file
• a refresh/update: only updating the value/status of each parameter

The second option is to be used for DAQ_Move and DAQ_Viewer because one doesn't want to trigger hardware issue because of this. But in order to implement this refresh, one need to make sure the current settings and the one from the file have the same structure. One has to create a compare method for that purpose, either has a member of Parameter (if we think we will propose that to pyqtgraph) or within the pymodaq.utils.parameter.utils module. (after giving it some thought, I vote for this last solution)

@Ashwolaa propose to tackle this

[seb5g]

done in #205