Filter button GUI inconsistency

[Josef Sábl]

I think that functionality of filters button should be changed around. I have mouse buttons and respective button actions in mind.

Standard GUI behaviour
======================
LMB: Default action, usually quite simple and straightforward
RMB: Additional and feature complete means to manipulate with given object

FZ Filters button - now
=================
LMB: Displays option dialog for filters with lots of settings
RMB: Turns filters on and off

FZ Filters button - should be
=================
LMB: Turns filters on and off
RMB: Displays additional and feature complete options for filters

Take Compare Button as an example, that one is implemented correctly.

Proximity of these two buttons along with their similar function but inconsistent behaviour makes them ergonomical nightmare as user needs to try what will actually happen when he l/r clicks one of buttons.

I use these buttons almost constantly and still don't intuitively remember what will happen if I left click the filter button.

[Jez McKean]

See also #5605