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
public final static int EXISTING_VARIABLE = 2;
    /**
     * Constant for defining this dialog as intended to edit an existing link
     * location (value = 3).
     */
    public final static int EDIT_LINK_LOCATION = 3;
    private IResource currentResource = null;
    /**
     * Constructs a dialog for editing a new/existing path variable.
     * 
     * @param parentShell the parent shell
     * @param type the dialog type: <code>NEW_VARIABLE</code> or
     * 	<code>EXISTING_VARIABLE</code>
     * @param variableType the type of variable that can be edited in 
     * 	this dialog. <code>IResource.FILE</code> or <code>IResource.FOLDER</code>
     * @param pathVariableManager a reference to the path variable manager
     * @param namesInUse a set of variable names currently in use 
     */
    public PathVariableDialog(Shell parentShell, int type, int variableType,
            IPathVariableManager pathVariableManager, Set namesInUse) {
        super(parentShell);
        this.type = type;
        this.operationMode = type;
        this.variableName = ""; 
        this.variableValue = ""; 
        this.variableType = variableType;
        this.pathVariableManager = pathVariableManager;
        this.namesInUse = namesInUse;
        if (operationMode == NEW_VARIABLE)
            this.standardMessage = IDEWorkbenchMessages.PathVariableDialog_message_newVariable;