For any application compilied to binary with camomile, currently, the datadir
With this patch, the datadir will be detected at runtime via environment
variables (by default), and if nonexistent, will fall back on
Camomile 0.7.x supports initialization by Functor. Use this.
Using environment variables has security issue. Data stored in datadir are simply unmarshalled therefore if a malicious user can control the location of datadir, he can cause anything, including buffer overflow.