verify
Description:
Verify if the key is signed and the signature matches the value and provides the aegis token which was used for signing the key.
    
Parameters:
| this | the Account. | 
| key | the name of the key or prefix of the keys to be verified. | 
| token | location to receive the pointer to aegis token. | 
Returns:
| true if the key is signed and the signature matches the value, false otherwise. |