Drymass

- enh: bump dependencies on qpformat, qpimage, and qpsphere
- improved file format support
- improved speed of in-memory operations
- several other minor fixes
- docs: minor cleanup

- enh: when using incomplete profile files, they are now merged with
(instead of overriding) existing profiles (drymass.cfg) in the
respective output directories (27)
- docs: minor update

- fix: pin scikit-image version to 0.14.0 because threshold_li has
changed (https://github.com/scikit-image/scikit-image/issues/3605)
- enh: implement "roi" configuration option "force" (8)
- ref: replace default config values of `nan` with `None` (13)
- ref: turn comments in definitions.py into real strings (23)
- docs: add automation tutorial (usage of profiles and scripts)

- fix: replaced hack for plotting units with better solution due
to incompatibility with tight_layout in matplotilb 3.0.2

- feat: implement profile management via `dm_profile` command and
allow to select profiles via the "--profile" command-line argument
in the command-line interface (20)
- fix: if time is unknown, write "nan" instead of "0" to the output
statistics file
- ref: explicitly use row-column coordinates in skimage's regionprops
(bump skimage version to 0.14.1)

- fix: do not create "_dm" results directory for root directory in
recursive analysis mode (19)
- docs:
- add DryMass logo
- update software description