Shapeout2

- feat: add background correction in quickview (54)
- fix: workaround for different plot widths due to title label (33)

- build: add pyinstaller hook for pyqtgraph

- fix: preferences dialog did not open in macOS App bundle (76)
- enh: disable R settings in preferences dialog if rpy2 is missing
- build: bump dclab from 0.29.1 to 0.32.4 (this should have happened
in the 2.5.0 release which introduced R-lme4 analysis)
- build: bump pyqtgraph to commit c1900 (post 0.11.1)
which mainly improves plot export (59)
- tests: introduce manual tests that require a human in "tests-manual"
- ref: key [calculation]: "emodulus model" is deprecated in dclab
- ref: use "lut_identifier" instead of deprecated "method" keyword when
retrieving isoelasticity lines

- feat: implement linear-mixed effects models with R/lme4 (55)
- ci: overhauled build process

- ci: fix rtd build
- fix: typo in infobox in analysis view (69)
- fix: macOS builds did not use our pyqtgraph fork (reported in 70)

- maintenance release