Merge pull request #207 from StefTweet/2.1

Updated at 14/11/2012 and 15/11/2012 of symfony / symfony-docs
translating cookbook/form/create_form_type_extension
minor tweaks after PR #207
Merge pull request #210 from gregquat/2.1

Fix typos + translation of cookbook/form/create_form_type_extension
Update from PR #212 by @jbcrestot
Update from #216 by @Gregoire-M
Updating from PR #217 by CedCannes
Merge pull request #215 from StefTweet/2.1

Updated at 16/11/2012 of  symfony / symfony-docs