logic: indexer count and fixes

* added option to define the amount of parallel indexers in the appsettings
* fixed unparsed files query in ASTVisitor
* fixed: to update a node's type in the storage the node does not have to be defined anymore

src/lib/settings/ApplicationSettings.h

@@ -47,6 +47,9 @@ public:
 	int getFontSizeStd() const;
 	void setFontSizeStd(const int fontSizeStd);
 
+	int getIndexerThreadCount() const;
+	void setIndexerThreadCount(const int count);
+
 	// code
 	int getCodeTabWidth() const;
 	void setCodeTabWidth(int codeTabWidth);