Shapeout2

- setup: bump dclab from 0.26.2 to 0.27.5 (support for machine
learning features)
- fix: modify the GUI to enable box filtering for ml_score_???
features
- ref: pipeline.get_features now only returns features that are
available (previously all features were returned when no
datasets were in the pipeline)

- fix: export file names were allowed to have invalid characters
- fix: Quick View showed filtered events that were not plotted
(statistics were computed correctly though)
- fix: Quick View was not very informative when all events were
filtered away - a message is now shown
- setup: bump dclab from 0.26.1 to 0.26.2 (fix bin num computation
using Doane's formula)

- fix: marker hue feature data min/max was always computed even if
not selected; for datasets without bright_avg (standard hue) this
resulted in long waiting times
- fix: avoid pyqtgraph error messages in pipeline plots by disabling
hovering events (not used anyway)
- fix: plot export did not work for single plots
- fix: exported event images sometimes had wrong contrast

- enh: add busy cursors wherever it seems fitting
- setup: bump dclab from 0.24.7 to 0.26.1 (volume-deformation
isoelasticity lines, improved DCOR caching)

- fix: opening sessions did not work due to missing slot decorator
- fix: in some cases the temperature/viscosity setting was not
correctly written to the UI for individual slots when switching
between slots with fundamentally different settings (e.g. channel
and reservoir)
- fix: KeyError when switching between slots with different
temperature options
- setup: bump dclab from 0.23.0 to 0.24.7 (equidistant isoelastics,
faster polygon filtering, crosstalk correction failed due to
improper configuration update since Shape-Out 2.1.1)

- fix: ValueError when trying to compute contour spacing, because no
datasets are selected for a plot
- fix: coloring scatter plot by feature did not work when the feature
contains nan values
- fix: search path in session should not be filename but its
directory
- setup: bump dclab from 0.22.5 to 0.23.0 (possible HDF5 export issue)