[orders] unified interface for all possible payments.
wip2
eol fix
[order] simplify things. remove money, currency, client classes.
[order] get rid of BaseCaptureOrderAction, intr FillOrderDetails request.
[order] add some tests.
[order] add tests for CaptureOrderAction.
[order] fix test on 5.3
[action] add basic get http request action.
[doctrine] add mongo and orm mappings for order model.
[order] add docs to payum/payum and payum/core
[order] update core's get-it-started.md
[order] update get-it-started docs of all supported payments.
[order] add link to the doc.
[order][doc] $registry -> $payum
[doc] fix typo