PoESkillTree.cs
   + Fixed 'main' to 'root' to correctly parse json
SkillTree.cs
   + added canSwitchClass
	parameters: string className
	return: true/false
   + added support for finding start nodes, their connecting nodes and who they belong to
ManWindow.xaml
   + added Name fields to each of the combobox options
MainWindow.xaml.cs
   + comboBox1_SelectionChanged now only resets tree if the
     selected class doesn't have it's nodes connected to the main tree