Integrate Samsung's Air Actions

This commit adds support for the stylus gestures supported by Samsung
S-Pen-compatible devices - the Air Actions. Air Actions is a middleware
supported in Galaxy Tab S6, Note 9 (partially) and Note 10, that
translates S-Pen gestures into keyboard events. (More information from
the developer documentation:
https://developer.samsung.com/codelab/air-actions/overview)

There are two parts:
1, an extensions for assigning the actions, configured from the Settings -> Configure Krita
dialog
2, Android packaging changes to enable interfacing with the Air Actions
middleware