Implement TrackerSparqlStatement consistently on all connections
This MR:
- Fixes tracker-statement-test so we actually test it on all given connections (By mistake only 1 was tested several times)
- Fixes tracker_sparql_statement_bind_datetime() on local connection statements
- Implements TrackerSparqlStatement for HTTP connections, based on TrackerSparqlParser and string substitution
- Tests that as well
This makes TrackerSparqlStatement consistent to use across all 3 types of TrackerSparqlConnection, which also comes in handy for SERVICE <http://...> {}
.