config: moving to separate unit
config: easier to read other types of values
config: add support for datapath
config: restructure sample a bit
config: show in env. which configuration is read
config: enable iniparser by default.

Suggest to use bundle if iniparser isn't available.
config: moving configuration globals
config: support for callback
config: set listen from config
config: support for setting privilege drop in config
update NEWS.
Merge branch 'config_improvements'

Fixes #5.