Add options for tied notes in tablature

[its-not-nice]

For tied notes in tablature we need three options:

• show ties and repeat fret numbers
• show ties only
• show nothing

The first and third options are covered by the on/off state of the existing "Show back-tied fret marks" setting, which this effectively replaces. The middle option is not currently available automatically.

Options for when a parenthesised fret number should appear during a tie (independent of the above setting):

• Never
• At the start of a system [current default]
• At the start of a new bar [not so common, but does exist in print]

And, independent of the above, an on/off setting for whether to show a parenthesised fret number during a tie when a marking is on or starts on it, e.g.:

This should be on by default.

(The exact wording and arrangement of these options, and the defaults for each tab style is TBD)

[its-not-nice]

Addendum:
Where a bent note is tied over a barline, a parenthesised fret number should be shown (unless 'Parenthesis indicating ties' is not set to 'Never show').

(here a (1) is required at the start of the second bar if the option is set to 'Always show at the start of a bar', for instance)