removed un-used PdoConnection class
added new transaction API. added initial tests.
Merge pull request #316 from robin850/master

Documentation update
Fixed test:prepare params for Postgresql

I don't know if anyone has run the tests, but I'm unable to pass the preparations. The tables are duplicated in each schema, they have multiple primary keys which are not included in foreign keys... Even after fixing the schemas, I receive fatal:
``
Propel\Generator\Exception\EngineException: Table "book" declared twice
``
port PR #704 from Propel 1.6
port PR #704 from Propel 1.6
Merge pull request #401 from staabm/transapi

Transaction API
Merge pull request #416 from auss/patch-2

port PR #704 from Propel 1.6
Merge pull request #415 from auss/patch-1

Fixed test:prepare params for Postgresql
fix failed jekyl compilation due to highlight tags
Merge pull request #419 from lunika/master

 	fix failed jekyl compilation due to highlight tags
change default locale from en_EN to en_US
Merge pull request #420 from lunika/default_locale

change default locale from en_EN to en_US
allow to use reference-only on external-schema tag
don't generate sql if skipSql equal true on parent table
on versionnable behavior, don't generate sql if parent table had skipSql
equal to true
create test for I18n behavior testing skipSql parameter
create test for Versionnable behavior, testing skipSql parameter
Merge pull request #422 from lunika/master

I18n, versionnable and external-schema fix issue