Command parser only do minimal check. now parameter value can be a sequence of non-space characters, or a string surrounded by quotation marks(these marks can be a part of the value string in escaped form)
   Make error message be more friendly.(if there is some error in parameter's value, the parameter name will be provided)
2. Refactor function login_to_cmdctl() in class BindCmdInterpreter.
   Avoid using Exception to catch all exceptions.

git-svn-id: svn://bind10.isc.org/svn/bind10/branches/trac220@2108 e5f2f494-b856-4b98-b285-d166d9295462