[sfFormExtraPlugin] added some information in the README file (closes #6630)
[sfFormExtraPlugin] added some information in the README file (closes #6630)

git-svn-id: ab26511c47a339431d6301e1a5fb68cf34c77940@24545 ee427ae8-e902-0410-961c-c3ed070cd9f9

nixilla/sfFormExtraPlugin,krzyc/sfFormExtraPlugin,Virtuvia/sfFormExtraPlugin,krzyc/sfFormExtraPlugin,Virtuvia/sfFormExtraPlugin,nixilla/sfFormExtraPlugin