Add ability to prioritise enabled converters

[tomdickman]

Currently there is no way to prioritise the converter usage when multiple converters are enabled, the factory just chooses the first enabled converter from a hard coded list.

It would be good if we were able to configure the priority of enabled converters in plugin settings, so that when the factory returns an instance, it is the highest priority enabled converter, as opposed to in order of an arbitrary hardcoded list.