Legend label positioning bug fix and PlotViewport refactoring
Button and text alignment fix in Lens Alignment tab
Fixed small merge conflict
acqmng: be lest crazy about high quality SEM acquisition

We were putting the settings so high that no user would ever actually use them (~5mn acquistion)

Note just x4 resolution and x4 dwell time. So it's "only" 16 x longer acquisition time.
gui canvas: on size event should be sent to _all_ interested overlays

any displayed overlay might be interested in knowing the size has changed.

fixes a bug with the dichotomy overlay not being the right size
gui settings: be more careful with ranges

make sure that the value is encompassed in the range

it was mostly aimed at solving problems with long exposure times in the acquisition window.
It didn't help, but still, it's an improvement
gui acquisition: update acquisition time whenever the streams are (de)selected

It'd be nice to subscribe to the stream tree, but it's not (yet) possible.

Also try harder to remove all streams that the view could be listening to, before destroying it.
Merge branch 'master' of vpn.delmic.com:odemis
gui plot canvas: simplify storing the current selected value

keep the info just via the val_x VA.
Also fix (a bit) the unit display, which might not always be meters (can also be px)

still need to fix the unit in the legend.