fix data path to do better than clt.nc and add units

get spatial bounds and array ranges and units into mongo
get temporal units and add stub that normalizes them (internals of
  which are intended to be replaced by udunits) so that we can
  interpret what times mean
wrap last to first point values to create missing implicit cell
wrap lats into -180..180
render in < 32000 point chunks for webGL limit and use cross chunk
  scalar ranges for colormaps
deal with mask values by turning them into NaNs and handling them
  in a javascript friendly way
Merge branch 'normalize_time' into next