Guitar tablature: zig-zag number style support

[ShibuyaCyana]

Task Description
Adding support for this zig-zag number style in tablature:

Examples:

(actually 2 guitars written in a same line)

I found this style especially common in books from Japan. Despite a little confusing to read at first, benefits of this style include:

1. Saving vertical space, especially important when making sheets for band with lots of guitars;
2. Font size could be larger, without vertically sticking together;
3. Line height among the six lines could become smaller, closer to a 5-line staff, which is aesthetically more satisfying.

[scorster]

Excellent request. I can readily envision times when I'd use zig-zagged tablature chord style.

+1