Changeset 2504 for branches/PluginInfrastructure Refactoring/HeuristicLab.PluginInfrastructure/Starter/SplashScreen.resx

Worked on core of plugin infrastructure.

• Collected all classes into a single assembly (HL.PluginInfrastructure)
• Moved SplashScreen and MainForm from HeuristicLab.exe project into the plugin infrastructure.
• Introduced namespaces
• Added strict access modifiers (internal)
• Fixed most FxCop warnings in plugin infrastructure core.
• Fixed issues with plugin load/unload events
• Deleted empty interface IControl

#799