Add non-GUI/headless livemon version.

The grgsm_livemon_headless.grc file can be re-created using grgsm_livemon.grc
and the instructions in the README, documenting how to disable the GUI in the
normal livemon version.

apps/README

@@ -15,3 +15,19 @@ There are following helper programs for grgsm_decode program:
 * grgsm_channelize (old name: gsm_channelize.py) - splits wideband capture file into multiple files - each contain 
                   single GSM channel.
 
+* grgsm_livemon_headless - command line version of grgsm_livemon.  It
+                  is created by changing grgsm_livemon.grc like this:
+
+                   - Change Options block->Generate Options from 'QT
+                     GUI' to 'No GUI'.
+                   - Set Options block->Run Options to 'Run to
+                     Completion'.
+                   - Remove the blocks 'QT GUI Range' (gain_slider,
+                     fc_slider, ppm_slider) and the 'QT GUI Frequency
+                     Sink'.
+                   - Change all occurances of <param>_slider to
+                     <param> in the XML file.
+
+                  After these changes are done, build the
+                  grgsm_livemon_headless python code using the grcc
+                  compiler.