Add Time Signature

Set time signature form the beginning of current measure.

This table contains supported time signatures and also their beam groupings.

Time signature	Beam grouping
2/4	2-2
3/4	2-2-2
4/4	4-4 and 2-2-2-2 (auto)
3/8	3
5/8	2-3 or 3-2 (user selectable)
6/8	3-3
7/8	2-2-3 or 3-2-2 (user selectable)
9/8	3-3-3
12/8	3-3-3-3

Set timesignature.

builder.setTimeSignature("2/4");
builder.setTimeSignature(2, 4);

Beam grouping (Theory.BeamGrouping) can be set for 5/8 and 7/8 time signatures.

builder.setTimeSignature("5/8", "2-3");
builder.setTimeSignature("7/8", "3-2-2");