Switch over to the ImageJ2 script editor

It's time to let the Fiji script editor retire...

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Fix Wiki URL

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
MediaWikiClient: fix cookie handling

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>