new builtin snippet to double current line or selection (issue #340)
improve behaviour: when c-d is pressed on empty line, content of previous line is copied
wip regen all symbols with LilyPond 2.18
better slashed grace icon
all symbols regenerated with lilypond 2.18
5 new barline icons
new barline types (fixes #365)

todo: fix kievan icon
fix barline kievan icon
add markup \\oval
rel import in ly
simplify socket naming. todo: test on windows