Requirements document updates

[ykarandikar]

• Make introduction more generic by removing reference to wallet and operating systems.
• Define digital credential and re-order general terms based on which term refers to another.
• Make use of Sender and Receiver mroe consistent throughout the document.
• Update discussion of Sender as provisioning entity scenario with more accuracy and consistency.
• Update the sequence diagrms that depict E2E sharing and sharing via intermediary to be more accurate
• Remove diagram that illustrated CarKey sharing using intermediary. It was duplicating information in the generic case.
• Simplify use cases
• Update the 3 scenarios of credential transfer for better accuracy and clarity
• Added a requirement about single redemption. I believe it's crucial for the problem at hand.
• General fixes to break long sentences into shorter ones.