Support more oob exchanges with attachments

[etschelp]

see: https://github.com/hyperledger-labs/business-partner-agent/issues/798

adds support for the following

Backend:

• [x] indy v2 credential offer
• [x] indy v1 presentation request
• [x] indy v2 presentation request
• [x] dif presentation request

Frontend:

• [x] indy v2 credential offer