Rewrote the config to a more rigid state

Resolves sddm/sddm#39

More configuration instances now available. Every instance is a separate class.

Sections are supported.

Serialization handled in a more sensitive way - does not remove comments.

Type handling is unified, using the QTextStream shift operators.

Probably the most overengineered configuration parser you've ever witnessed.
Which values are you talking of?
StateDir was added because it's planned to keep more sddm state stuff in it - currently the X auth files are kept in it, and it's the home directory for the sddm user.