Merge pull request #7 from Kaffeine/master

Tools: Small improvements in forms.
World generation moved to python.
New class WorldGenHook: world generation handler, can be extended by python.
Remove invalid module import.
CheckBox inherits from Button.
New widgets - RadioButton and RadioButtonGroup
Some documentation.
Tiled Line.
Bugfix in vector operations.
Fix segfault in Sprite/NinePatch.
Change parenthood behavior.
Parent cannot be setted directly.
Smart pointers in SystemPlanetWidget.
Initial race support.
Race relations parsing.
More info of HabitablePlanet in InfoWidget.
Race icon in InfoWidget.
SpaceInfoWidget -> InfoWidget.
More info of System in InfoWidget.
SolarSystem -> PlanetarySystem
Some improvements in planet styles.
Doxygen improvements.