Shapeout2

- enh: display session file name in window title
- setup: drop support for older numpy versions
- setup: bump dclab from 0.39.9 to 0.39.13 (fix visualization of
the "ml_class" score when the ml_score features contain nans)

- fix: implement closeEvent in main and ask user before exiting
- fix: fix possible failure during update check
- fix: show a message box when the R version is incompatible (114)
- ref: only reload R/lme4 information in preferences when the
corresponding tab is selected to avoid preferences lock-up (114)
- tests: use hidden settings variable to skip asking the user to
clear the session
- setup: bump dclab from 0.39.5 to 0.39.9

- setup: bump dclab from 0.39.3 to 0.39.5 (fix opening files
with some online filter settings)

- enh: add button "Find best spacing" in Plot tab in Analysis View
that iteratively finds sane spacing values (110)
- enh: notify user in plot if contour spacing is too large (110)
- enh: add action to remove all datasets from a session (97)
- fix: mysterious behavior of subclassed pg.ColorBarItem (109)
- setup: bump dclab from 0.39.1 to 0.39.3 (increased verbosity,
renamed feature labels, refactored DCOR access)

- feat: add support for extensions in the form of loading dclab
plugin and machine-learning features (85)
- setup: drop support for Python 3.7
- setup: bump dclab from 0.37.2 to 0.39.1

- fix: wrong scale for viscosity in bulk emodulus computation (104)
- fix: save unused polygon filters in sessions (101)
- fix: allow to delete polygon filters (100)
- setup: bump dclab from 0.37.0 to 0.37.2 (enhanced speed for
operations involving contour computation)