more flat_button refactoring.  try centering the gain and peak displays
even more flat_buttons
Standardize drawing of PixFader and BarController; implement flat_buttons and prelight.
Prepare for using Controllable interfaces, instead of passing in Adjustments.
ToDo:  reimplement image caching in a standardized way across widgets
move preferences->GUI->Metering into its own tab
Make sure all our VC projects agree that the product is called 'Mixbus3' (as opposed to just 'Mixbus')

It'd be nice if we could use 'ARDOUR::config_dir_name' for this purpose (or perhaps 'PROGRAM_VERSION'). However, neither is implemented widely enough at present to make this practical. Keep an eye on them though, as possible future strategies.
Add an extra folder to get searched (on Windows only) when looking for config files.

This is a preliminary test to find out if 'All Users' would be a better place for our (writable) config files, as opposed to the user's personal 'AppData' folder (which we used in Mixbus2). N.B. this should not effect any previous operations on Windows or non-Windows platforms.
replace missing fader redirect color
brighten post-fader redirects, and change redirect leds to blue
Fix ArdourButton event sequence.
Always give ArdourButton a chance to handle Press or Release events if you override them.
This allows ArdourButtons to do the "Pressed" animation
And it now correctly eats the event so button clicks don't select the channelstrip.
add option to blink rec-enables
More fixes to ArdourButton actions.
Optionally allow events to fallthrough to parents, in particular for the DnDVBox case.
Also allow the number_label to operate as a track selector.
remove offset from icons when button is pushed
video-timeline tools path updates for OSX and Windows
fix plugin bypass button action
yet another ArdourButton action tweak
processor toggle controls should be blue when activated
use 2 digit width as minium for track number labels
experiment with unicode circle for rec-en

fixes button-area width mismatch on track-headers
except for tape-tracks (which till use old fixed size icon)
amend 7be3c88a, update rec-en color
ArdourButton: suppress visible response if no action is defined.

This fixes issues where the button is used as Label
(currently track-numbers and meterbridge track-name)