Both GDM and GNOME uses DConf to manage its own configuration. Extract
the common dependencies into a separate role called "dconf".
DConf provides:
- creating empty directories for configuration
- handler to apply configuration when configuration has changed
Add ability to install the GNOME desktop environment.
Most common global settings (date and time, power management, touchpad settings, theme) can be configured via Ansible variables.
See "group_vars/all" file.
