add payex payment factory.
add a check that lib installed to skip gracefully.
[payex][payment-factory] add agreement related api and actions
[payex][payment-factory] configure status actions for payment and agreement.
[action] add some missing action for auto pay logic.
[payex] add missing actions recurring, sync etc.
fix  merge of configurations defined in different configs.
[payex] add doc.
[doc] add doc about payment done action.
[doc] tweek a bit.
[doc] fix link
[doc] tweek a bit.
[doc] fix doc.
[payex] use stable version of the lib.
Merge pull request #30 from Payum/payex-payment

add payex payment factory.