Move to new plugin architecture

[joshmoore]

Do we need to additionally start testing wit the new engine?

We recommend moving your plugin to the new plugin architecture as soon as possible. The conversion process is simple and is explained in this guide - note that this is all still a work in progress however, and there may be frequent changes made to the docs.

The testing process for plugins should not change however, save for needing an explicit dependency on npe2, for now.

Originally posted by @DragaDoncila in #26 (comment)

[joshmoore]

cf: tlambert03/napari-omero#34