Move subsurface-core to core and qt-mobile to mobile-widgets

Having subsurface-core as a directory name really messes with
autocomplete and is obviously redundant. Simmilarly, qt-mobile caused an
autocomplete conflict and also was inconsistent with the desktop-widget
name for the directory containing the "other" UI.

And while cleaning up the resulting change in the path name for include
files, I decided to clean up those even more to make them consistent
overall.

This could have been handled in more commits, but since this requires a
make clean before the build, it seemed more sensible to do it all in one.

Signed-off-by: Dirk Hohndel <dirk@hohndel.org>

core/pluginmanager.h

@@ -0,0 +1,19 @@
+#ifndef PLUGINMANAGER_H
+#define PLUGINMANAGER_H
+
+#include <QObject>
+
+#include "isocialnetworkintegration.h"
+
+class PluginManager {
+public:
+	static PluginManager& instance();
+	void loadPlugins();
+	QList<ISocialNetworkIntegration*> socialNetworkIntegrationPlugins() const;
+private:
+	PluginManager();
+	PluginManager(const PluginManager&);
+	PluginManager& operator=(const PluginManager&);
+};
+
+#endif