Various issues from the first test

[Myramong]

• Adding a segment only adds a segment on the ui, not to the song object.
• Clicking an empty cell n the track editor crashes the program (issue with the code for dragging, array out of bounds). Clicking the track editor without a segment selected causes the same crash.
• The dropdown menu in the Edit Command window defaults to no command, clicking save causes a crash.
• Note parameters can't be set anywhere (the commands that affect note duration)
• Removing a song segment causes a crash.

Feedback:

• Make the track editor Double buffered to reduce flicker.
• When drawing commands on the track editor, It might look better if the command's parameters are drawn below the name of the command. This would fix the ugly overlapping text, I think.
• Notes should be moved out of the Edit Command drop down list. Maybe a grid of buttons would look better.
• Call subroutine is a powerful command, but currently there's no way to define subroutines.

[KatDevsGames]

Current TODO: Finish subroutine support. Alternate UI for adding notes.