Make a tutorial: how to port my plugin

[ctrueden]

We should make a tutorial that shows how to port a simple IJ1 plugin. For instance one could create an IJ2 plugin that relies on the legacy service. It would have a Display output. The run() method would be cut and paste from the IJ1 plugin. At the end the created ImagePlus would use legacy service to create associated display. (even calling registerImagePlus if you want to keep bidirectional translation in place)

Test that this approach would work and fix issues until it does.

Migrated-From: http://trac.imagej.net/ticket/1375