PATCH: add uml state machine generators

[Tomas Pospisek <tpo2 sourcepole ch>]

Hello Dia'lers,

I've taken Unai EstÃbanez Sevilla's code generator [1] for
Dia UML state machines to text, abstracted it slightly and
added a C code generation "plugin" [2].

The "pimped" code generator now creates a hash with states and
a list of transactions, that are easier to work with when
generating state machine code.

Unai's original "text" generator has become a "simple" addon
as is the newly done C generator.

I'd be very happy if the UML state machine generators could
be included in the Dia distribution/repository.

* base STM infrastructure:
  http://www.sourcepole.ch/assets/2012/6/5/uml_stm_export.py

* C code generation:
  https://www.sourcepole.ch/assets/2012/6/5/uml_stm_c_export.py

* "text" generation:
  https://www.sourcepole.ch/assets/2012/6/5/uml_stm_text_export.py

Please let me know if the code needs changes before inclusion.

Thanks a lot to you all for making Dia possible!
*t


[1] https://mail.gnome.org/archives/dia-list/2009-July/msg00005.html
[2] http://sourcepole.ch/2012/6/5/generating-state-machines-with-dia