Plugin fixes jul2014

+Fix on closing plugin windows: plugin really stopped.
+Added settings to documenting with Doxygen (file "Doxyfile"). Started some documenting on EmulationCore/Propeller.cs, GUI/Emulator.cs, GUI/PluginEditor.cs, etc.
just my opinion, but I just don't see any benefits of short form, dropping brackets.
Thus I would use always
```csharp
if (smth)
{
  doSomething();
}
```

rather than omitting them.