- Use qhelpgenerator-qt5 instead of qcollectiongenerator-qt5 to
build help files as the latter has been superseded by the former
beginning with Qt 5.12.
- Remove an unnecessary build file that was included in the help
directory.

- Update to version 10.11:
- Display warning if function points are not well defined
(gh#markummitchell/engauge-digitizer#288).
- Handle large dynamic range in documents with four axis points
(gh#markummitchell/engauge-digitizer#296).
- Ensure there is always at least one curve
(gh#markummitchell/engauge-digitizer#294).

- Update to version 10.10:
+ Curve Fit window shows higher order polynomial fits
(gh#markummitchell/engauge-digitizer#287)
+ Grid removal is faster and more accurate
(gh#markummitchell/engauge-digitizer#285,
gh#markummitchell/engauge-digitizer#284)
+ New command line feature to extract original image
(gh#markummitchell/engauge-digitizer#277)

- Update to version 10.9:
- Linux installer ensures installation is into a new directory
(gh#markummitchell/engauge-digitizer#275)
- More protection against inconsistent inputs
(gh#markummitchell/engauge-digitizer#274)
- More protection against inconsistent data in input files
(gh#markummitchell/engauge-digitizer#273)