Dclab

- fix: cast data to float when filling with nan values when checking the
size of ancillary features
- fix: dclab-split did not work when nptdms is not installed
- tests: skip tests that require nptdms, requests, or rpy2 if those
- enh: add check to warn users from setting None-type config values
packaages are not installed
- tests: add test for non-scalar plugin feature
- ci: run tests with different setup.py-extras installed

- fix: use temporary file names during CLI operations

- fix: workaround for when rpy2 finds R_HOME, but R doesn't

- fix: slicing of non-scalar features for hierarchy children (128)
- fix: passing a directory to the CLI tdms2rtdc did not work
- enh: support slicing of non-scalar features for DCOR data (132)
- enh: support slicing of the contour feature for HDF5 data (132)
- enh: support slicing of LazyContour for contour AncillaryFeature (132)
- enh: minor optimizations of the DCOR format
- ref: raise NotImplementedError for futile attempts to slice the image,
contour, or mask features for .tdms data (132)
- ref: cleanup CLI code
- tests: increase coverage of CLI (116)

- enh: introduce user-defined "user" configuration section (125)
- scripts: refactor fem2lutiso_std.py and fem2iso_volume.py so that
model-specific post-processing is done in hooks named after the FEM
identifier, e.g. fem_hooks/LE-2D-FEM-19.py (90)
- docs: new LUT data version 10.6084/m9.figshare.12155064.v3
- ref: minor code cleanup

- feat: introduce user-defined plugin features (105)
- fix: dclab-verify-dataset now also prints other errors it encounters
- fix: installing the "lmer" R package failed, because "statmod" was not
installed
- fix: correct data types for "fluorescence:sample rate",
"imaging: roi position x", and "imaging: roi position y" (124)
- enh: support new .rtdc attribute "online_contour:bg empty" which is
True when the online background image is computed only from frames
that do not contain any events (124)
- enh: `AncillaryFeature` now populates other ancillary features when they
share the same method (104)
- enh: dclab-verify-dataset now returns a non-zero exit code if there
were errors, alerts, or violations (120)
- ref: streamlined dataset check function for missing meta data keys