configuration and script file to generate doxygen html content

[mMerlin]

Initial configuration file and script to generate stand alone doxygen html content in a sibling folder to fritzing-app. Only on a linux system. I do not have a windows (or mac) environment available to create and test the script. The Doxyfile should be valid everywhere.

Needs doxygen installed and available in the standard shell search path. Currently generates 940M of content.