- moved all build-time options to Makefile.config
- build VILLASnode without hook support
- build VILLASnode without web & API support
- build VILLASnode without IO format support
- build VILLASnode without external plugins
The notion of "VILLASnode" / "external program" is removed from the
interface. Now there's only a distiction regarding which process opened
the object first, and this is handled transparently by the functions.
This enables some new uses for the interface, for example connecting
two instances of VILLASnode or two instances of DPsim directly.