This pull request is a subset of #6490
This adds a new library for creation of applications based on Qt Quick
framework.
It contains reusable QML / Qt Quick components based on QGIS core
library.
The initial work introduces MapCanvas
To enable compilation of the library, use WITH_QUICK=TRUE
Further documentation of the library is located in doc/qgsquick.dox
For background information see the associated QEP:
qgis/QGIS-Enhancement-Proposals#109
The initial implementation is largely based on the work of Matthias Kuhn
and Marco Bernasocchi on QField probject - kudos to them for the great
job!
