Closes #667

* Add confirmation dialog for Remove All

* Show Remove All confirmation dialog only when clicking the action

* Add confirmation dialog for New File as well

* Simplify slot_fileNew

* Tweak return indentation

* Remove slot_ prefix and decoration

* Create midi-channel-ab.c

midi-channel-filter.c + bits of midi-split.c = an attempt at a per channel output A/B routing

* Update Makefile for ab plugin

* Update midi-channel-ab.c

fixed incorrect copy/paste

* add A/B plugin

* Add A/B plugin

* Add A/B plugin

* Add A/B plugin

* Add A/B plugin

* Rename and reorder binary options

* Fix output order

* Fix order(?)

* Fix order

* More efficient code, floats to booleans, comparison fixes

* Revert mistake

* Fix midi output port numbers

* Fix maker name

* Add copyright header line

* Add confirmation dialog for quitting Carla

* Make exit confirmation dialog configurable

* Don't save confirmExit in the host object

* Don't set host.confirmExit in loadHostSettings either

* Modify .ui file using qt4 designer

* Change config ui back to original size

* Put check for exit prompt on multiple lines

* Convert (not ==) to (!=)

Triggered by 8b1fd1f537
Closes #655

Closes #640

Fixes #653

Fixes #635

Merge as much as possible stuff from second loop to first. Use second
only to set width and X for ports.

More folding
Clean some magic height changes. Bottom space now consists of
max(port_spacing, port_spacingT) + border width - trailing port_spacing.
Port types are traversed in loop, using array.

First stage of refactoring.
Fixed indentation of line, added in visual correction of lineHinting
effect.

Use single rect through all drawing sequence (change of decrement in one
place affects all next steps).

By shifting border inside of logical bound, free space around is
increased by one line weight.

Same as for main canvas - 2d cursor is aligned to pixels. Visible
difference is different look of antialiased map itself.

Current implementation fills outest pixels incompletely, making slightly
blured look.

When box is moved in scaled state, coordinates get random fraction,
which breaks border-to-pixel alignment.