Fix #9780 Display line layers in Road Graph settings
Merge pull request #1127 from 3nids/fix8873

better message display in map edit tools (fix #8873)
Merge pull request #1242 from p0cisk/roadgraph

Fix displaying line layers in Road Graph settings (fix #9780)
helper for setting combobox and button to display fields and expression dialog
use QgsExpressionGuiHelper in labeling gui
UI to define vector layer display expression in layer properties
make displayField deprecated