gui canvas: added checks, so tab_data.tools won't be accessed if it's not present.
gui model: stream ROI only set when stream is active

it's noticable with the SPARC which has multiple SEM streams with different ROI.
gui lens align: fix A/B move computation

according to theoritical axis convention.
Still need a real trial to check it's really correct.
Merge branch 'master' of vpn.delmic.com:odemis
gui: fix overlay selection with Y inverted

Ensure after every conversion that the top/bottom and left/right are correctly ordered,
so that if Y is in opposite direction, it doesn't aftect the code. It also fixes some
corner cases when the user was dragging to redimension a selection from one side to the
other side.

Also clean up code in RepetitionSelectionOverlay by keeping functions small.
gui: remove unused code for advanced range slider

we ended up just using 3 controls connected via the VAs