Bug 576670 - Add ability to label objects during debugging

Provide a way to assign labels to variables in the debugger and display
the labels later in all places where labelled object may appear (debug
hover, Expressions view etc).

Added new (internal) API in org.eclipse.jdt.debug.core -
IJavaObject.setLabel(String) and IJavaObject.getLabel().

JDIModelPresentation/JavaVariableLabelProvider is used. The labelled
object is shown with bold text and configurable color, the label is
prepended to the variable value and there will be an optional 'Label'
column in Variables view just to display labels.

Change-Id: I830ef64a5e8d85c2c621dbc6a1b50598881e8c75
Reviewed-on: https://git.eclipse.org/r/c/jdt/eclipse.jdt.debug/+/186570
Tested-by: JDT Bot <jdt-bot@eclipse.org>
Reviewed-by: Andrey Loskutov <loskutov@gmx.de>
22 files changed