Add loadxml/savexml commands and textbox gui dialog.

Docs/README.commands

@@ -77,6 +77,16 @@ save - save properties to an XML file
   file: the name of the file to save, relative to the current
     directory (defaults to "fgfs.sav").
 
+loadxml - load XML file into property tree
+  filename: the path & filename of the file to load
+  targetnode: the target node within the property tree where to store the XML 
+  file's structure
+
+savexml - save property tree node to XML file
+  filename: the path & filename for the file to be saved
+  sourcenode: the source node within the property tree where the XML file's 
+  structure is assembled from.     
+    
 panel-load - (re)load the 2D instrument panel
   path: the path of the XML panel file, relative to $FG_ROOT (defaults
     to the value of /sim/panel/path if specified, or

Docs/README.gui

@@ -358,5 +358,26 @@ Example:
    <max>360</max>
   </dial>
 
+textbox
+-------
+
+The text will be retrieved/buffered from/within a specified
+property tree, like:
+
+<textbox>
+    <!-- position -->
+    <x>100</x>
+    <y>100</y>
+
+    <!-- dimensions -->
+    <width>200</width> 
+    <height>400</height>
+
+    <property>/gui/path-to-text-node/contents</property>
+
+    <slider>15</slider> <!--width for slider -->
+
+    <editable>true</editable> <!-- whether the puLargeInput is supposed to be editable -->
+</textbox>  
 
 __end__