Align Rests With Notes

dot.js :: change position of dots for dotted rests

formatter.js :: Add functions to align rests with notes.

stavenote.js :: add function to determine rest position for a note group

tables.js :: add options to note glpph duration_codes for positioning
dots on dotted rests.

tuplet.js :: Align rests with tuplet notes. Move lower bracket closer to
stems.

vex.js :: add functions to find mid point between two lines

flow.html :: add rests_tests

rests_tests :: new test for aligning rests with beamed and tuplet notes