Added text selection and copy support to TextFieldWidget.

Use Shift and navigation key (cursor, home, end) to select a portion of
text, and replace/delete/cut as appropriate.
Also provides support for selection with mouse (click and drag)

mods/cnc/metrics.yaml

@@ -6,3 +6,4 @@ Metrics:
 	CheckboxPressedState: true
 	ColorPickerActorType: fact.colorpicker
 	ColorPickerRemapIndices: 176, 178, 180, 182, 184, 186, 189, 191, 177, 179, 181, 183, 185, 187, 188, 190
+	TextfieldColorHighlight: 800000