Clean up UI elements

"New File" button now indicates "Batch" also.  Hide
experimental fields (can be re-enabled using Java
preferences).
Rename plugin

Was labeled 'Spectral Lifetime Analysis', went to
'Spectral Lifetime Imaging (SLIM)', e.g. the
SLIM plugin.
Handle degenerate cases in batch histogram

Fixed problems when all bin counts were zero.
Merge remote-tracking branch 'origin/tidy-up'

Hides experimental features from UI.  Adds lifetime.lut for
development.  Fixes batch histogram issue when there
are no counts.