* Save more data to QML
* Virtual fields
* Map tips
* Display expression
* Read only flag
* Streamline expression context generation
Whenever an object is able to generate an expression context it
implements the method createExpressionContext() declared in
QgsExpressionContextGenerator.
This makes a cleaner API and allows using QgsFieldExpressionWidget and
QgsDataDefinedButton from python because standard OO programming
approaches are used instead of callbacks and void pointers.
* Colorize output of doc and sip tests
* Fix build
* Fix sip complaints
* Fix rebase problems
* Workaround failing bindings test
Rationale:
- there was a lot of large objects passed by value, so potentially
there's a speed bump from this
- even for implicitly shared classes like QString/QList there's still
a (small) cost for copying the objects when there's no reason to
- it's the right thing to do!
