CellWorx: ignore thumbnails and missing channel names

Any TIFF files with "_thumb_" in the name are now ignored, so that
thumbnails are not inadvertently picked up.  If channel names are
missing from the .htd file, then the channel names stored in the
.pnl/.tif files will be used instead.
Add planeInfo=true support to FakeReader

In order to investigate recent connection lost issues, being able
to generate a large number of plane info objects and insert them
into OMERO would be useful.

See: https://www.openmicroscopy.org/community/viewtopic.php?f=5&t=7351&start=20
Replace planeInfo by exposureTime

In order to have the planeInfo elements actually filled
in OMERO, an of the fields need be non-null making the
planeInfo boolean unnecessary.
Merge pull request #795 from joshmoore/fake-plane-info

Add planeInfo=true support to FakeReader
Merge pull request #746 from melissalinkert/metamorph-screens

CellWorx: ignore thumbnails and missing channel names