Add GRMustache v6.8.2
Initial import of doctool prototype
Set the minimum Xcode version for the generate docset

Require at least the major version associated with the docsetutil binary
used to generate the docset. This prevents older Xcode versions from
loading the docset and likely crashing as a result.
Make docset tokens compatible with Xcode 4

Xcode 4 needs an explicit NodeRef to the containing page.
Fix whitespace
Touch the doc set package directory when generating output

The directory may have already been created by a previous run.
Merge branch 'master' into doctool-prototype
Fix accidental absolute path reference to GRMustache dependency.
Merge branch 'doctool-prototype'