Backends: Remove extraneous SetBackend-function.
Backend test: Small cleanup.
LevelDB: Clean up naming somewhat.
Misc: Go vet clean.
Makefile: Run `go vet` by default.
Query: First draft of graphite-compatible query engine.

The parser is built using the Ragel parser-generator, so that will be
needed in case any changes has to be made to the actual parser.
Makefile: gofmt ragel output.
Parser test: Build better example data.
Parser: Remove the initial toy parser.