This eponymous virtual table is able to decompose the full database
in all its composing triples. This may be used to implement queries
with predicate variables in a generic way, and finally support the
kind of queries where we gave up (e.g. "select * { ?s ?p ?o }").

Internally it works by using the TrackerOntologies in order to
split the query into a set of queries for individual
properties/columns, some optimizations happen when specific matches
are given, and the SQLite engine does take care of the ones we don't
optimize, sorting, etc...

This virtual table will also be useful in the future when implementing
CONSTRUCT/DESCRIBE commands.