Refs #2480 - Show further information in prop widgets.

* Show icon when workspace is about to be replaced.
* Show icon when value has been restored from a previously-entered value.
Merge branch 'feature/2480_show_required_props_and_default_vals_in_alg_diags' into develop

Conflicts:
	Code/Mantid/MantidQt/API/CMakeLists.txt

Refs #2480.