More flexible tool API
Minor code format fixes
Clipboard freeze fixed(?)
Arrow correcly growing close to the start point
Improve maintainability
Add undo/redo stack
Updated dbus API. Now it sends a signal with every capture, it may
be captureFailed or a captureTaken which contains the raw image
bytes in png format. You have to add an id to the screenshot calls
so it will be returned as a way to know the origin of the signal.
