io.nds.auth_connect: connection convience function

    - moved kerberos-protected connection from TimeSeriesDict.fetch into
      io.nds
Channel{List}.query_nds2: new channel query methods

    - NDS-based analogue to CIS query methods
Channel: improved __repr__
TimeSeriesDict.fetch: added verify kwarg and use ChannelList.query_nds2

    - verify=False skips the find_channels call, might become default,
      maybe add DeprecationWarning in the future
    - fetch() method now uses ChannelList.query_nds2 instead of
      hand-built query method if verify=True