[Web UI] Added simple check for valid IPv6 address received in GET request:
- string should be longer than 7 characters
- string should be shorter than 40 characters
- string should have at least three ":" characters
- fifth character from string should be equal to ":"
- string should contain only allowed characters (:0123456789abcdefABCDEF)
The same check is used during loading the list of hosts from file.