Expand a bit the qnet documentation (#5373)

* Expand a bit the qnet documentation

* Expand a bit jigsaw.xml by describing how to create an initial control network

* Update the qnet documentation blurb

Author: oleg-alexandrov

isis/src/control/apps/jigsaw/jigsaw.xml

@@ -39,6 +39,12 @@
       converges and the <b>UPDATE</b> parameter is selected.
     </p>
 
+    <p>
+      The input control net may be created by finding each image footprint with <b>footprintinit</b>,
+      computing the image overlaps with <b>findimageoverlaps</b>, creating guess measurements with 
+      <b>autoseed</b>, then registering them with <b>pointreg</b>.
+    </p>
+
     <p>
       Optional output files can be enabled to provide more information for analyzing the results of
       the bundle. <b>BUNDLEOUT_TXT</b> provides an overall summary of the bundle adjustment;

isis/src/qisis/apps/qnet/qnet.xml

@@ -30,6 +30,10 @@
     </p>
 
     <p>
+      This program is an ISIS GUI application. To run it, type its name in a
+      terminal, with no arguments. This will start a blank session, having the
+      main Qnet window and the control network navigator window.
+
       There are 3 core windows used in this application.
     </p>