Added UI.md to doc/

doc/UI.md

+USER INTERFACE
+==============
+
+Button states
+-------------
+If the HTML Form has no modifications, the `Close`, `New` and `Delete`
+buttons are enabled. The `Save` button is disabled. 
+  
+If the HTML Form has modifications, the `Save`, `Close`, `New`, and
+`Delete` button is enabled. No button is disabled.
+
+
+Save Button 
+-----------
+
+* User presses the Save button
+  1. Reset all validation states
+  1. Client validates HTML Form
+  1. Form is submitted to server
+	 * Success: 
+		 1. Show message provided by server
+		 1. Current formelements and data will be reloaded.
+		 1. Process server reponse 'redirect':
+			* 'client': No redirect.
+			* 'no': No redirect.
+			* 'url': Redirect to URL
+	 * Failure: Happens on communication errors, if data validation
+       fails, form actions fails or saving data fails.
+	     1. Show error message.
+         1. Client: Ignore server reponse 'redirect'. Client stays on current page.
+    
+
+Close Button
+------------
+* User presses the Close button
+	1. Form not modified by user: Client redirects to previous page.
+	1. Form modified by user: Ask User 'You have unsaved changes. Do you want to close?'
+       * Yes: Client redirects to previous page.
+       * No: Client stays on current page.
+       * Save & Close: 
+		 1. Client reset all validation states
+		 1. Client validates HTML Form
+		 1. Client submits form to server.
+			* Success: Process server response 'redirect':
+			  * 'client': Client shows previous page.
+	          * 'no': No redirect.
+              * 'url': Redirect to URL
+		    * Failure: Happens on communication errors, if data validation
+	          fails, form actions fails or saving data fails.
+			  * Show error message. 
+			  * Client: No redirect. Ignore server reponse 'redirect'.
+
+Delete Button: Main record
+--------------------------
+* User presses the button. Ask User 'Do you really want to delete the record?
+  * Yes: 
+    * Delete record on server.
+    * Process server reponse 'redirect':
+      * 'client': Client redirects to previous page.
+      * 'no': Error message.
+      * 'url': Redirect to URL
+  * No:
+    * Client does not delete record on server.
+    * No redirect. Client stays on current page.
+
+New Button
+----------
+* User presses the button
+  * Form not modified by user: Client redirects to href url.
+  * Form modified by user: Ask User 'You have unsaved changes. Do you want to save first?'
+    * Yes:
+      * Client reset all validation states
+      * Client validates HTML Form
+      * Form is submitted to server
+        * Success:
+          * Client: Ignore server reponse 'redirect'. Client redirects to href url.
+        * Failure: Happens on communication errors, if data validation fails, form actions fails or saving data fails. 
+           * Show error message.
+           * Client: Ignore server reponse 'redirect'. Client stays on current page.
+    * No: 
+      * Client does not save the modified record.
+      * Client redirects to href url.
+    * Cancel:
+      * Client does not save the modified record.
+      * Client stays on current page.
+  
+
+File Handling: Upload
+---------------------
+* No previous uploaded file present
+  1. User presses the Browse button
+    1. User selects file
+      1. File is uploaded to qfq immediately
+      1. Browse button gets disabled and hidden
+      1. File delete button is shown
+    1. User cancels file selection
+      1. no action
+* Previous uploaded file present
+  1. User deletes file
+    1. File delete button gets disabled and hidden
+    1. Browse button gets enabled and displayed
+