Text editing convenience functions for null content lines

[craigsapp]

Keyboard shortcuts should be added to insert lines of null data, interpretations, and local comments to a text file.

Probably along the lines of: control-alt-N to add a row of null tokens above the current line, and control-alt-shift-n to add a row of null tokens below the current line. Likewise control-alt-i for a null interpretation line, and control-alt-L for a null local comment line. The number of fields added would be equal to the needed number in the file at that line (including any changes after the line caused by spine manipulators).

This will be useful when added layout commands, or inserting notes into a score — particularly for large scores.

Example:

Starting with this content where the cursor is on line 4:

Typing control-alt-shift-L would generate this content:

or typing control-alt-n would generate this content: