Add first version of bend.ly (valid for lilypond 2.14)

bend.ly - created by Marc Hohl - is an experimental implementation of bends.
The ultimate goal is adding a new engraver for bends in the core of lilypond.
Follow this issue for updates:
https://code.google.com/p/lilypond/issues/detail?id=1196
bend.ly revised by Thomas Morley to make it work on 2.16

See https://code.google.com/p/lilypond/issues/detail?id=1196#c8
Merge pull request #15 from fedelibre/bend

Bend