Fractional sharp notation

VERY WIP (I'll move it to the main namespace if it's finished.)

This notation is mainly intended for equal temperaments

Accidentals

Prime limit	Comma	Sharps
5	81/80	1/5
7	64/63	1/4
11	33/32	1/2
13	1053/1024	1/2
17	4131/4096	1/8
19	513/512	1/34
23	736/729