Dclab

- cli: write warning messages to logs in tdms2rtdc
- ref: increase verbosity of warning messages

- fix: discard trace data when "samples per event" has multiple values
for tdms data
- fix: prefer image shape over config keywords when determining the
shape of the event mask and check the shape in dclab-verify-dataset
- fix: avoid ContourIndexingError by also searching the neighboring
(+2/-2) events when the contour frame number does not match (67)

- enh: explicitly check contour data when testing whether to include
the first event in tdms2rtdc

- ref: convert said ValueError to ContourIndexingError

- fix: ValueError when verifying contour frame index due to comparison
of float with int

- feat: new command line script for creating a scalar-feature-only
dataset with all available ancillary features "dclab-condense"
- enh: enable scalar feature compression for hdf5 export
- docs: fix doc string for dclab-tdms2rtdc
(`--include-initial-empty-image` falsely shown as "enabled by default")