Made step to remove ASyncWindow in favour of usage of Future and FutureWatcher.

This should allow concurrency in the plugins to be independent from their container.

Contains also some work on the system for registering plugins.

pglab/plugin_support/ToolbarLocation.h

@@ -0,0 +1,19 @@
+#ifndef TOOLBARLOCATION_H
+#define TOOLBARLOCATION_H
+
+#include <QString>
+
+class ToolbarLocation {
+public:
+	ToolbarLocation();
+	ToolbarLocation(QString toolbar, QString group, int position = -1);
+
+	bool isEmpty() const;
+private:
+	QString m_toolbar;
+	QString m_group;
+	int m_position = -1;
+};
+
+
+#endif // TOOLBARLOCATION_H