Use [Shift]+[-] to input 破折號 as default

- In order to enter 破折號 easier, set em dash as default.

- Add "―" (horizontal bar) and "﹋" (wavy overline)

- Remove the followeing symbols to avoid misuse:
	"ˍ" (modifier letter low macron)
	"╴" (box drawings light left)
	"﹣" (small hyphen-minus)

- Tune the order of candidates
Merge branch 'symbol' of github.com:hiunnhue/libchewing into symbol