Add environment configuration

[George3d6]

The mindsdb server should run some environment configuration upon installation.

• Create /var/mindsdb/ directory that contains config.json which can be used to configure lightwood, mindsdb, mindsdb_server... etc.
• Add the daemon file to wherever the specific OS stores daemon file and do any OS-specific configuration to the daemon file
• Add a default directory structure to /var/mindsdb/ for storing datasource, predictors and anything else that might need storing.