Issues with Zarr output chunk sizes

[forman]

Fixed some issues with Zarr output chunk sizes given by process parameter rechunk: (#12)

• Fix: New chunking can now overlap multiple chunks in input (Dask chunks).
• Introduced new chunk size value "input" which forces using chunk sizes from input.

Now I can use for Calminos L3:

process:
  rechunk:
    "*":
      lon: 2880
      lat: 1440
      time: 1
    lon: null
    lat: null
    time: 365
    time_bnds:
      time: 365
      bnds: 2