Validation, improved UX, error messages for Add ref.

Author: Layoric

src/ServiceStackIDEA/.idea/workspace.xml

@@ -9,7 +9,7 @@
       <maximumSize width="550" height="220"/>
       <minimumSize width="400" height="220"/>
       <opaque value="true"/>
-      <preferredSize width="550" height="220"/>
+      <preferredSize width="550" height="300"/>
       <requestFocusEnabled value="true"/>
     </properties>
     <border type="none"/>
@@ -67,7 +67,7 @@
         <children>
           <component id="e88c4" class="javax.swing.JTextPane" binding="errorTextPane">
             <constraints>
-              <grid row="1" column="0" row-span="1" col-span="1" vsize-policy="6" hsize-policy="6" anchor="0" fill="3" indent="0" use-parent-layout="false">
+              <grid row="1" column="0" row-span="1" col-span="1" vsize-policy="2" hsize-policy="2" anchor="0" fill="3" indent="0" use-parent-layout="false">
                 <preferred-size width="150" height="50"/>
               </grid>
             </constraints>