Use 6-code Checksum for Quick Search of Grin Relay Address

[garyyu]

Please read the Grin Relay Address Scheme, we have the 6th part as the checksum for the Grin Relay address.

For example, in address tn1-qvgsq0kd-7gvgqksg58fkqm9-ms5cplcllev4fnw-svevuqs2jukrtrc-guuvze, the last part guuvze is the so-called 6-code checksum.

For the convenience of the user, we can provide a Quick Search service: user can input the last 6-code part to launch a searching on Grin Relay server, and the Grin Relay server can return the complete address (or more than one in some rare cases), and use can confirm or pick one as the receiver address.

This feature will be useful for the case which need use manually input the receiver's address and release the pain of this long address format.

Note:

• For the security, the application MUST remind the user to confirm the returned full address IS the correct receiver address!
• If the receiver is NOT online, in most cases we don't search that receiver's address. But even we get the right search result, it DOESN'T mean the receiver is online at this moment.

[garyyu]

Closed by #3