Groups cannot be deleted from disk & db in standard mapfile.

[jlap]

A group created in a standard mapfile cannot be deleted. It can be removed from the rendering by removing the include line in the map editor. But the file will remain on disk and in the database.

Standard mapfile need a delete interface a bit like the scribe one. It can be simplified though, since reordering the layers can be simply done by reordering the include statements.

[jlap]

Fixed in babb041a8ecb1fcef8d56a55c74a533a63e38e1b

For standard mapfiles, I added a minus button next to the dropdown. Clicking it calls the map's removeGroup function, and deletes the INCLUDE 'layers/filename' line from the map editor and then saves.