Experimental tweak for the "Object Constraints" tab so that it now shows a warning message instead of the "Add Constraints" button when the active object is in Pose Mode. Hopefully this will further alleviate any confusion over Object vs Bone level constraints. Todo: While coding this, I noticed that we currently don't have any way of making help-text labels in UI panels which can span multiple lines (word-wrapped or manually split). Probably not a critical issue, but it would be nice for completeness...