coverage assessment of Turtle in the test suite

[ericprud]

Before finishing RDF 1.1 CR, I attempted to understand the coverage of Turtle by looking for particular patterns in the test suite. (I did the same thing for SPARQL but haven't dug it up yet.)

The process was:

• create a yacker grammar for the langauge (I didn't pick that name)
• mentally traverse the grammar, identifying features and combinations of interest (the hard part).
• map those to XPaths over the yacker parser results
• mechanically produce HTML report

Documenting here in case folks want to keep that up. One could, e.g. encode Ruben's IRI tests in the paths file, but it may not be worth it.