preview-mode: Add lilypond-version-switch

Add a function/predicate 'lilypond-greater-than?' that
can switch the program flow based on the currently
run Lilypond version
preview-mode: Finish color-voices

Clean up file.
use \temporary with LilyPond > 2.17.5
preview-mode: Finish color-directions

- Incorporate latest fixes by David Kastrup
  - Now works from 2.16.1 onwards
- Clean up file
preview-mode: Finish debug-layout-options.ly

Small cleanup touches
preview-mode: Finish display-control-points

- Clean up file
- Apply workaround for Ties in 2.17
  with lilypond-version-switch
- Remove configuration arguments
  Now configuration is done completely through variables,
  this makes the function calls much simpler
preview-mode: Finish display-grob-anchors

File cleanup
preview-mode: Finish display-grob-names

File cleanup
preview-mode: Hide work on Preferences UI

The work on the UI for the configuration Preferences
is postponed to a future release.
Instead of completely reverting the stubs already done
this commit simply hides them so they aren't executed and displayed