add storage functions

sim/state/storage.ts

@@ -0,0 +1,20 @@
+
+namespace pxsim.storage {
+
+    export function putValue(key: string, value: string) : void {
+        sessionStorage.setItem('simulatorValue_'+key, value);
+    }
+
+    export function getValue(key: string) : string {
+        if(sessionStorage.getItem('simulatorValue_'+key)) {
+            return sessionStorage.getItem('simulatorValue_'+key);
+        } else {
+            return "";
+        }
+    }
+
+    export function remove(key: string) : void {
+        sessionStorage.removeItem('simulatorValue_'+key);
+    }
+
+}