Bug 298835 Merge e4 Project Path Variable back into the 3.6 stream
The virtual folder and filters changes are already in 3.6, the project path variable changes in e4 still remains to be merged.
bundles/org.eclipse.ui.ide/src/org/eclipse/ui/internal/ide/dialogs/PathVariableDialog.java
/**
     * The value of the variable being edited.
     */
    private String variableValue;
    /**
     * The original name of the variable being edited. It is used when testing
     * if the current variable's name is already in use.
     */
    private String originalName;
    /**
     * Used to select the proper message depending on the current mode
     * (new/existing variable).
     */
    private int operationMode = 0;
    /**
     * Reference to the path variable manager. It is used for validating
     * variable names.
     */
    private IPathVariableManager pathVariableManager;
    /**
     * Set of variable names currently in use. Used when warning the user that
     * the currently selected name is already in use by another variable.
     */
    private Set namesInUse;
    /**
     * The current validation status. Its value can be one of the following:<ul>
     * <li><code>IMessageProvider.NONE</code> (default);</li>
     * <li><code>IMessageProvider.WARNING</code>;</li>
     * <li><code>IMessageProvider.ERROR</code>;</li>
     * </ul>