Add reference {REF...} support for otp field

[betsythefc]

Summary

Some services use Symantec VIP, and when that is generated, it can work for multiple services. It would be helpful to put a reference in the otp custom attribute to the entry for Symantec so I only need to update one otp entry if things need changing.

Examples

Right now, it seems the otp uses the {REF} string as the secret, and doesn't follow the field reference.

Context

(see Summary above)

[stefan123t]

Just found this after logging my own, new feature request under #6782
@droidmonkey please decide which one to keep open for your great work. Thanks!
@betsythefc you can work around this issue by referenceing the referenced password from another entry (usually username/password is the first step) in the TOTP auto-type sequence (second step) and use the local {TOTP} reference together.
instead of this in your first username/password entry
{USERNAME}{TAB}{PASSWORD}{ENTER}{DELAY 3000}{REF:<FIELD>@<SEARCH_IN>:<SEARCH_TEXT>}{ENTER}
use e.g. the following in your second TOTP entry
{REF:U@<UUID>}{TAB}{REF:P@<UUID>}{ENTER}{DELAY 3000}{TOTP}{ENTER}
This is somewhat like reverse polish notation for auto-type sequences.