gui: ensure zoom always goes out of x1

due to float errors, zooming with shift might stuck around x1.
Fix that by using an epsilon.
andorcam2: improve comment
model: add TODO
model: add some more metadata
andorcam3: allow to change gain

also improve how binning and resolution are checked when set
simplify binning API support -> only support latest API
add baseline metadata
fix test when AOI not available