px_process_airframes: add image path as optional argument for markdown output

usage:
./px_process_airframes.py -m -i ../image/path

Tools/px_process_airframes.py

@@ -1,7 +1,7 @@
 #!/usr/bin/env python
 ############################################################################
 #
-#   Copyright (C) 2013-2015 PX4 Development Team. All rights reserved.
+#   Copyright (C) 2013-2017 PX4 Development Team. All rights reserved.
 #
 # Redistribution and use in source and binary forms, with or without
 # modification, are permitted provided that the following conditions
@@ -35,10 +35,11 @@
 #
 # PX4 airframe config processor (main executable file)
 #
-# This tool scans the PX4 source code for declarations of airframes
+# This tool scans the PX4 ROMFS code for declarations of airframes
 #
 # Currently supported formats are:
 #   * XML for the parametric UI generator
+#   * Markdown for the PX4 dev guide (https://github.com/PX4/Devguide)
 #
 #
 
@@ -67,6 +68,12 @@ def main():
                         metavar="FILENAME",
                         help="Create Markdown file"
                              " (default FILENAME: airframes_reference.md)")
+    default_image_path = '../../assets/airframes/types'
+    parser.add_argument("-i", "--image-path",
+                        default=default_image_path,
+                        metavar="IMAGEPATH",
+                        help="HTML image path for Markdown (containing the airframe svg files)"
+                             " (default IMAGEPATH: "+default_image_path+")")
     parser.add_argument("-s", "--start-script",
                         nargs='?',
                         const="rc.autostart",
@@ -108,7 +115,7 @@ def main():
     # Output to markdown file
     if args.markdown:
         if args.verbose: print("Creating markdown file " + args.markdown)
-        out = markdownout.MarkdownTablesOutput(param_groups, args.board)
+        out = markdownout.MarkdownTablesOutput(param_groups, args.board, args.image_path)
         out.Save(args.markdown)
 
     if args.start_script: