data: saving errors to Storage

* saving errors in separate sqlite table
* use MessageShowErrors to show the errors in the UI
* show error count permanently in the right side of the status bar with click to show
* fixed clicking of error locations
* fixed expanding of files with errors

src/lib/data/Storage.h

@@ -203,9 +203,6 @@ private:
 	mutable std::map <FilePath, Id> m_fileNodeIds;
 	HierarchyCache m_hierarchyCache;
 
-	TokenLocationCollection m_errorLocationCollection;
-	std::vector<std::string> m_errorMessages;
-
 	mutable SearchResults m_cachedResults;
 	mutable std::string m_cachedQuery;
 };