[PATCH] conflation plugin fix and improvement (sort, selection)

[Tyndare]

I tried to update the conflation plugin, my modifications include:

• enabling checkstyle for Eclipse project
• listen to layer removal event to avoid referencing removed layers
• clear conflation data if plugin is hidden/shown again
• allow sorting of conflation match cases table (e.g. sorting by "Score" or "Distance" column)
• listen to DataSet selection to select the corresponding match case if it exist.
• always recreate the toggle dialog in the ConflationPlugin.mapFrameInitialized. I hope this will fix #13182 and #14136
• fix primitivesRemoved() event handler and rewrote ConflateMatchCommand, I hope this will fix #13066

I have a doubt on the way I rewrote the class ConflateMatchCommand. The sub-commands are
not built in its constructor as previously, but only in executeCommand(). It was the only way
I found to make undo/redo work without errors when I conflate at the same time two different buildings with two other buildings that share nodes.

Don't hesitate to tell me if you think my patch need rework.

Thanks

[Tyndare]

PATCH

[Tyndare]

I finally identified the undo/redo bug as being due to a problem in the AddPrimitivesCommand which has been fixed by #14410.

I've updated my patch and submited it as a pull request on github:
​https://github.com/JOSM/conflation/pull/4

[Don-vip]

Merged, thanks!