Various changes: code refactor and new vops
Four different changes:
- some classes/members/routines renamed as requested in !545 (merged)
- simplified fix for !566 (merged)
- added
proposal_pay_operation
to cover half of the issue #325 - added
collateralized_convert_immediate_conversion_operation
requested on Mattermost:CoreDev (and possibly earlier in some issue) to cover lack of information about amount of HBD received (such info was included infill_collateralized_convert_request_operation
vop, but that one only shows up after couple of days)