Add 'add' rev proxy feature, list az in table

The 'add' button in the reverseProxyPanel
will default to the az with the fewest reverse
proxies and allow the user to choose and instance type.
Then it creates the instance and adds it to the necessary target group.
A few utils were added to also fetch the availability zones

java/com.sap.sailing.landscape.common/src/com/sap/sailing/landscape/common/AzFormat.java

@@ -0,0 +1,9 @@
+package com.sap.sailing.landscape.common;
+
+import java.io.Serializable;
+
+public enum AzFormat implements Serializable{
+        MIXED,
+        NAME,
+        ID; 
+}

java/com.sap.sailing.landscape.common/src/com/sap/sailing/landscape/common/SharedLandscapeConstants.java

@@ -75,4 +75,19 @@ public interface SharedLandscapeConstants {
      * of a typical process instance.
      */
     int DEFAULT_NUMBER_OF_PROCESSES_IN_MEMORY = 4;
+    
+    /**
+     * Indicates that an instance only acts as a reverse proxy. ie. it is not hosting other services.
+     */
+    String DISPOSABLE_PROXY = "disposableProxy";
+    
+    /**
+     * The tag name for a target group which contains all the instances running httpd.
+     */
+    String ALL_REVERSE_PROXIES = "allReverseProxies";
+    
+    String IMAGE_TYPE_REVERSE_PROXY = "disposable-reverse-proxy";
+    
+    String CENTRAL_REVERSE_PROXY_TAG_NAME = "CentralReverseProxy";
+
 }