fixed a bug of mailbox option configuration at imap-append command.
short descriptions each commands are added to help message at help command.
short advice is added to unknown command error message.
server command help messages.
imap-append command help messages.
fixed a bug of  mailbox rename method to global db API.
internal saved id value should be but a string, not a number.
Merge branch 'rename'
protocol decoder. UTF-7 mailbox name at select command.
protocol decoder. UTF-7 mailbox name at examine command.
protocol decoder. UTF-7 mailbox name at create command.
protocol decoder. UTF-7 mailbox name at delete command.
protocol decoder. UTF-7 mailbox name at rename command.
protocol decoder. UTF-7 mailbox name at subscribe command.
protocol decoder. UTF-7 mailbox name at status command.
protocol decoder. UTF-7 mailbox name at append command.
protocol decoder. UTF-7 mailbox name at copy command.
Merge branch 'rename' into utf7_mbox_name
ruby debug option at unit-test task of Rakefile.
Merge branch 'test_task'
Merge branch 'test_task' into utf7_mbox_name