Modernize dialog construction

[johnjohndoe]

The TrackList class currently constructs dialogs using deprecated methods such as onPrepareDialog, onCreateDialog, showDialog. The DialogFragment class should be used instead.

I started the migration with the track renaming dialog on this work-in-progress branch.
@rcgroot Please let me know if you want me to continue with the remaining dialogs. If you have some other implementation in mind please comment here or inline on the branch code.

[rcgroot]

I've my plans set on https://github.com/rcgroot/open-gpstracker-ng which connects to the service and content provider of this current app.The UI is completly new and has much more modern libraries.

[johnjohndoe]

I have to admit I haven't quite understood what are you aiming at in the new project. When it started I thought this would be a wear app. When I install it now I am ask to install the former application. If you find the time it would be great if your put a basic roadmap in the README.md of the repository.

[johnjohndoe]

Just in case: I rebased the branch onto the latest commit on develop.