Add slur notation for hammer-ons/pull-offs

[ckoppelman]

Description
When I read sheet music, I normally see legato notated with a slur, and tablature marked with either an #h# or #p# or a slur ligature. For example:

In Power Tab Editor, there's a slur on the tab, but it's missing the slur on the standard notation:

I would love to see a slur for a hammer-on/pull-off, so I can easily move read either tabs or notation (this is especially useful for someone playing the music with a different instrument like voice or piano).

[cameronwhite]

Yep, I agree this would be a nice improvement 👍