[sfPropelActAsPolymorphicBehaviorPlugin] Minor documentation fixes.
[sfPropelActAsPolymorphicBehaviorPlugin] Minor documentation fixes.

git-svn-id: a1664fd12af9af5ae16986e55917c3f79e67732b@7530 ee427ae8-e902-0410-961c-c3ed070cd9f9

Symfony-Plugins/sfPropelActAsPolymorphicBehaviorPlugin