DB/Guild: Fix incorrect input length limits

There are two incorrect field lengths related to guilds in the database, which can be used to cause an overflow client-side, by sending CMSG_GUILD_RANK and CMSG_GUILD_INFO_TEXT with long strings.

The name of a guild rank has a client-side limitation of 15 characters. If the length exceeds the client's limit the Guild Control dialog becomes unusable.

The guild information has the same 500 characters client-side limit as the guild bank tab information, but on server-side it can be 65k characters long. A lengthy guild info makes the whole Guild panel unusable.

Length of the other fields match the client's limits in the database: guild bank tab name (16), public note (31), officer note (31), motd (128), guild bank tab info (500).