#807942, #807982, #809936, #810010, #811294, #811266 by dereine: Backport quite a lot of handler tests.

#972620 by dereine: Add an administrative title field for all handlers to make it more possible to distinguish similar fields from each other in the UI.

#927270 by Cyberwolf: Allow the "options callback" for the in_operator filter handler to also have an "options argument" in the definition.

#958312 by tim.plunkett: Exports could have extraneous whitespace when exported from other modules like features.