[MIDI] Feature suggestion: remember last-used playback offset

[pimlottc]

When writing or debugging a score, it's useful to use the MIDI playback feature to start from a specific point. When working on a particular section, it would be useful if the "Play from..." command remembered the last time offset used and provided it as a default. It can also be pre-selected, so that if the user wanted to enter a new offset, they could just start typing and it would erase the previously used offset.

Proposed scenario

Suppose I am working on a section 1 minute and 2 seconds into the piece.

1. I run "MIDI Playback: Play from..."
2. The time offset input dialog appears, with no current value
3. I enter "1:02" and hit enter
4. the MIDI score plays from 1:02
5. I made some changes to that section of the score
6. I run "MIDI Playback: Play from..."
7. The time offset input dialog appears, with the value "1:02" already entered and selected
8. I hit "enter"
9. The MIDI score plays from 1:02
10. Satisfied with this section, I start working on an earlier section and make some changes
11. The time offset input dialog appears, with the value "1:02" already entered and selected
12. I enter "0:33" and hit enter
13. The MIDI score plays from 0:33