Rename triple* -> quad* files
Remove quadfix
Rename triple entities were relevant
Simplify method name
Simplify godoc
Add basic support for mongo testing

This is not intended to be for general consumption at this stage; it
requires that the tester has a mongod instance running and because of
the time taken to load the db, $GOROOT/src/cmd/go/test.go must be
modified to allow for tests longer than 10 minutes. A future CL may
allow db probing and the use of an existing cayley test dataset.
Make hashOf a function
Merge pull request #148 from kortschak/renaming

Renaming triple-related entities to the quads they actually are (eg, TripleStore -> QuadStore)
Remove non-documentation lint

Because of extensive nature of changes, tested all three non-memstore
backends - passed.
Quieten deadcode
Run go vet

Bugs found.
Merge pull request #149 from kortschak/lint-vet

Delinting, deadcode removal and vetting
Replace DebugString with Describe

This change makes tree description completely open to mechanical
analysis and ensures consistency between description formats for each of
the iterator types.

Renamed StatsContainer.(Kind -> Type) for consistency.
Convert Type fields to use graph.Type

Add text encoding methods to replace string storage.
Merge pull request #152 from kortschak/describe

Replace DebugString with a well defined type returned by Describe
Ensure we don't examine empty token

Fixes issue #163.
Merge pull request #166 from kortschak/issue163

Ensure we don't examine empty token
Don't retain results where the value is empty

Empty quad terms are not valid, so we should be able to safely drop any
results where the value is "".
Merge pull request #167 from kortschak/issue165

Don't retain results where the value is empty