An application dock applet for the MATE panel.

The applet allows you to:
* Place a dock on any MATE panel, of any size, on any side of the desktop you desire.
* Pin and unpin applications to the dock.
* Rearrange application icons on the dock.
* Launch applications by clicking on their icons in the dock.
* Minimise/restore the running application windows by clicking the applications dock icon.
* Detect changes in the current icon theme and update the dock accordingly.
* Use an indicator by each application to show when it is running.
* Optionally, use multiple indicators for each window an application has opened.
* Use either a light or dark indicator that it can always be seen no matter what colour the panel is.

This version contains following patches:
- Use xdg_data_dirs for desktop files lookup (https://github.com/ubuntu-mate/mate-dock-applet/pull/217)
- Move run-application hotkey to gsettings (https://github.com/ubuntu-mate/mate-dock-applet/pull/218)