Don't manipulate StelSkyCultureMgr's signals outside of the class

Although technically this works, architecturally it's unclean since it
breaks incapsulation (which technically doesn't exist since the signals
are public since Qt5, but this is only because of language limitations).

src/core/StelSkyCultureMgr.cpp

@@ -106,6 +106,11 @@ void StelSkyCultureMgr::init()
 	setCurrentSkyCultureID(defaultSkyCultureID);
 }
 
+void StelSkyCultureMgr::reloadSkyCulture()
+{
+	emit currentSkyCultureChanged(currentSkyCultureDir);
+}
+
 //! Set the current sky culture from the passed directory
 bool StelSkyCultureMgr::setCurrentSkyCultureID(const QString& cultureDir)
 {

src/core/StelSkyCultureMgr.hpp

@@ -147,6 +147,8 @@ public slots:
 	//! @param id the sky culture ID.
 	//! @return true on success; else false.
 	bool setCurrentSkyCultureID(const QString& id);
+	//! Reload the current sky culture
+	void reloadSkyCulture();
 
 	//! Get the type of boundaries of the current sky culture
 	//! Config option: info/boundaries

src/core/modules/ConstellationMgr.cpp

@@ -152,8 +152,7 @@ double ConstellationMgr::getCallOrder(StelModuleActionName actionName) const
 
 void ConstellationMgr::reloadSkyCulture()
 {
-	StelSkyCultureMgr* skyCulMgr = &StelApp::getInstance().getSkyCultureMgr();
-	emit skyCulMgr->currentSkyCultureChanged(skyCulMgr->getCurrentSkyCultureID());
+	StelApp::getInstance().getSkyCultureMgr().reloadSkyCulture();
 }
 
 void ConstellationMgr::updateSkyCulture(const QString& skyCultureDir)