Changes in DNF-2 compared to DNF-1

CLI changes

Reintroduction of YUM's configuration options `includepkgs` and `excludepkgs`

Due to a better compatibility with YUM, configuration options include and exclude were replaced by the original options includepkgs and excludepkgs.

DNF group install `--with-optional` option

Installation of optional packages of group is changed from subcommand with-optional to option --with-optional.

Python API changes

All non-API methods and attributes are private

Warning

All non-API methods and attributes of documented modules are now private in order to accomplish more distinguishable API.