Added possibility to apply "LIMIT 0" in PostgreSQL adapter

This is possible in Postgres and may be useful. "OFFSET 0" seems useless but I think it should be added for consistency.
[Runtime] removed unused use statements as detected by SensioLabsInsight
Merge pull request #431 from marcj/pimp-testsuite2

Pimped testsuite, session 2
Merge pull request #432 from hhamon/cleanup_dead_code

[Runtime] removed unused use statements as detected by SensioLabsInsight
Merge pull request #433 from marcj/add-sqlite-migration

Added SQLite migration, schema and foreignKey support.
Fix ProfilerStatementWrapper usage in ProfilerConnectionWrapper
Fix indeterministic ordering in OnDemandFormatterTest
a virtual column can return NULL value therefore
hasVirtualColumn method must use array_key_exists insted of isset
add testing for hasVirtualColumn with a null value
Merge pull request #435 from etienneroudeix/master

fix NULL virtual column problem
Use classname instead of FQCN
Rename getStatementWrapper to createStatementWrapper
Merge pull request #434 from gigablah/connection-wrapper

Fix ProfilerStatementWrapper usage in ProfilerConnectionWrapper
issue #427 fix, use symfony/validator ~2.2 again
Renamed NameGenerator to NameGeneratorInterface to match the CS
Merge pull request #437 from lunika/master

issue #427 fix, use symfony/validator ~2.2 again
Merge pull request #438 from mpscholten/master

Renamed NameGenerator to NameGeneratorInterface to match the CS
Merge pull request #404 from zergu/patch-1

Added possibility to apply "LIMIT 0" in PostgreSQL adapter
[Generator] made some simplifications
Merge pull request #439 from hhamon/model_refactoring

[Generator] made some simplifications