* Add a Jump to Time dialog
This implements #827 by adding a context menu entry to open a dialog
that allows the user to input a time/position to seek to for the current
song.
* Use callback interface for JumpToTimeDialog position submission
* Automatically show soft keyboard for JumpToTimeDialog
* Automatically move to next EditText in JumpToTimeDialog
* Crash if JumpToTimeDialog is started by wrong activity
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