gui: PolarOverlay label positioning update
model: add possibility to use thread instead of process in createNewContainer()

Not used yet, but will allow easier debugging of the backend
gui acqmng: don't merge streams for time estimation

optimisation only.
Should give more or less the same result.
gui stream: improve SEM/AR Stream to have smooth acquisition

reduce overhead by using synchronization Event.

For now done in a very ugly way. Need at least to have a generic code for the 2 types of synchronised acquisition.
It'd be even better if the whole code was in odemis.acq, instead of odmeis.gui!
tiff: increase floating point precision

for small numbers, the default 6 decimal precision could lead to very large error.
Directly noticeable when acquiring AR images on a grid.

So increase to 15, hopefully reducing the error to unoticeable epsilons.
gui: PolarOverlay tweaks and fixes
tiff: make sure the position metadata is read from OME if available

copy paste error lead to never read the OME metadata, causing very bad rounding error on the value.
gui stream: ensure SEM AR acq removes synchronisation when the acquisition is over

with the synchronisation enabled, the other code will be unable to get any image.
Merge branch 'master' of vpn.delmic.com:odemis