OLLib: Add editorialToolbox (start)

The editorial toolbox adds support for
- visually marking editorial additions 
- in-source communication (commenting) between editors

As a start this commit provides inSourceCommunication.ily
as well as its complementing Draft Mode files
and the editorialToolbox.ily entry point
OLLib: Add Draft Mode (basic concept)

Draft Mode is an essential concept within OLLib.
This commit provides definitions of used colors
and the main entry point.
OLLib: Add main (full) entry point

Include OLLib/full.ily to access the whole library