fix Quantity warning for new astropy
Channel: fixed dtype and added from_nds generator
io.nds: fixed NDS fetch, added auto-kinit

    - fixed syntax for nds2.connection.fetch, including checking for
      channels in nds before fetching
    - method to call kinit on the command-line
Spectrum: more explicit setting of Quantities
io.nds: remove old nds file in favour of folder
spectrum.psd: more explicit setting of Quantities
plotter: many updates

    - moved TimeSeriesPlot to new module, same syntax, different innards
    - improve formatting for time-axis ticks and values
TimeSeries: many small bug fixes

    - fixed Quantity setting
    - fixed TimeGPS usage
TimeSeries.fetch: more robust auto-fetcher

    - many small changes to make the auto-server fetch mechanism more
      robust