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.
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
Fix cs
Revert "Merge pull request #404 from zergu/patch-1"

This reverts commit 5df1067b4e6d03d165c83b761eb78f1fdbf6db1e, reversing
changes made to 58a25ded43c3d04313cad2b738342d307988b1b5.
fixed typo

see https://github.com/propelorm/Propel2/pull/433#commitcomment-3907618
Merge pull request #442 from staabm/tablediff

fixed typo
[Generator] Decoupled the Model and XML schema representation by introducing a new XmlDumper object.
Merge pull request #441 from hhamon/schema_dumper_feature

[Generator] Decoupled the Model and XML schema representation by introdu...
[Generator] [Builder] fixed syntax errors in builders
Fixed `getPlainSelectedColumns` so it returns no column aliases with aggregate functions.
Merge pull request #444 from marcj/master

Fixed `getPlainSelectedColumns` so it returns no column aliases with agg...
Merge pull request #443 from hhamon/fix_syntax_errors

[Generator] [Builder] fixed syntax errors in builders
[Generator] [Model] added unit tests for the TableDiff class and made some refactoring in the diff API.
[Generator] [Model] fixed phpdoc
Merge pull request #445 from hhamon/diff_testing_cleanup

[Generator] [Model] added unit tests for the TableDiff class and made so...