Plot canvas bug fix
gui comp: move minsize requirement of the AxisLegend to the component itself

The minimum size is due to its content, so let the component decide.
Sample holder registration function
Merge branch 'master' of vpn.delmic.com:odemis
config: prepare changelog for the new release
Check if holder is already registered
registeredSampleHolder VA initialization
Merge branch 'master' of vpn.delmic.com:odemis
driver phenom: also update registeredSampleHolder on insertion of a new sample holder

Simplify a bit by putting all the code related to sample holder into _updateSampleHolder()