Remove origImg

* scripts/run-pipeline.py (img): We don't need origImg given that we pass a
TimeStreamImgage throughout the pipeline.
Refactor derandomization

Handling everything on a single table made the code too complex and error prone.
We now handle three tables: (i) a time stream table, (ii) a csv table and (iii)
a master table.
* util/derandui.py: Refactor in order to use three tables instead of one.
* util/derandui.ui: Likewise.
Use closest existing timestamp

* timestream/manipulate/pipecomponents.py (DerandomizeTimeStreams.refreshMids):
Subject
Add ability to see derandomized image.

* util/derandui.py (DerandomizeGui._showPrev): New method to show a preview of
the derandomization.
(PanZoomGraphicsView): Activate this class so we can pan and zoom the preview
image.
Allow netcdf4 versions equal or greter than 1.1.0

* setup.py (install_requires): Subject