unify sys definitions in doxygen docs

[zippy]

Currently they are split into 3 pages, they should be unified into one page so context is preserved.

• update base_defs.pl to generate one file
• create css so the definitions look decent

[zippy]

as of 10f28fd93276 the code generates them as one file. They are pretty ugly, over to you Art to do some css magic. Generated file is: http://zippy.github.io/ceptr/ref_sys_defs.html

[artbrock]

• [x] Test of GHM tasklists
• [ ] Another one
• [ ] Yet another