script sem bleach: few fixes

fix CCD ROI being in the wrong side of Y and wrongly centered (bug found by Aaro)
Add support for light power (from Aaro)
driver semcomedi: add fastpark option

allows to force the scanner to park the ebeam as soon as possible

Needed by Aaro, should not be used for normal usage.
semcomedi: support resolutions up to 4096 px

Several people asked for it. How good it is depends actually on the precision of the hardware,
but that might work with our DAQ cards (NI 6251).

Also add another scale to the GUI so that we still support down to 256x256 resolution
driver semcomedi: try harder to find a fitting dwell time

first try with a read period as close as possible from the (requested) write period.
That should avoid having nothing between 800ns and 1.6µs dwell times.
Still need to try on real hardware.
acq align: fix CCD ROI position computation

Was a copy of the sem bleaching script, so needs the same fix.
In practice, it was not affecting the results because the ROI on the CCD
was always centered.