Remove credential and credential proposal

[guilherme-funchal]

• Allow removal of credentials from a person's wallet.
• Include credential proposal to user

[guilherme-funchal]

Hello Ian, The improvements to this "pull request" are :

52 Remove a credential

90 Tests if credential exists

92 Only one credential

Missing translate phrases Usability improvement Include icon to credentials

I tested it on my "master" version and the minor errors were fixed before sending. I think it would be good for you to test again.

Thank you

[guilherme-funchal]

Hello Ian, I am sending the credential proposal commits.