allow configure several storages.
update doc.
[di] restrict to use only class as storage entry.
add container aware registry.
[di] set registry as payum service.
remove context interface, lazy context etc.
[di] multiple storage

* configuration changes
* Abstract payment\storage factories.
* Remove context, add registry.
fix paypal pro payment name.
fixes bugs after refactoring.
update capture docs
Merge pull request #19 from Payum/multiple-storage-configuration

[WIP][di][factory] allow configure several storages.