[factory] add a separate factory for be2bill_onsite payment.
[doc] update be2bill onsite doc.
[be2bill] fix be2bill onsite factory tests.
add be2bill onsite factory to bundle.
Merge pull request #131 from Payum/be2bill-onsite-factory

Be2bill onsite factory
Merge branch '0.8' of git://github.com/Payum/PayumBundle