dev/core#2141 - Add support for token-tagging to all grant flows

dev/core#2141 - Add support for token-tagging to all grant flows

Suppose you have a downstream app/module -- such as the Civi-IMAP app/module.  It needs to store a notation which says
"this thing in our data" (e.g.  `civicrm_mail_settings`) "corresponds to that token in the OAuth data".

It can put a tag on the token (`tag=civicrm_mail_settings:123`) and use that for lookup

```
$tag = `OAuthSysToken.refresh +w tag=civicrm_mail_settings:123`
```

The advantage of this is that it's simple, flexible, and doesn't require new schema.

Of course, it's not end-all/be-all.  It's OK for 1:1 relationship.  But if
you want 1:M or M:M, then you'll have to model that as something else.  But
for basic usage, tags are simple and moderately flexible.