Added data structures in datagen_db.php to make it simpler to generate different frontend views.

Other changes:
1. Modified dotgen_argument.php, dotgen_hw.php, dotgen_inferred.php, dotgen_observed.php to use these data structures.
2. Modified header.php to unserialize the newly added data structures from datagen_db.php.
3. Added doxygen.config file and changed README.md as well as datagen_db.php, dotgen_argument.php, dotgen_hw.php, dotgen_inferred.php, dotgen_observed.php to output doxygen documentation.
4. Added xml directory with collection of xml scenario files. New IPAN scenarios also included here.