logic: improved performance of initializing the fulltext search index

* implemented using multithreaing for building the fulltext search index
* also: decreased ideal thread count by 1 to keep the machine responsive while indexing and building the index

src/lib_gui/utility/utilityApp.cpp

@@ -156,7 +156,7 @@ OsType utility::getOsType()
 
 int utility::getIdealThreadCount()
 {
-	return QThread::idealThreadCount();
+	return std::max(1, QThread::idealThreadCount() - 1);
 }
 
 bool utility::saveLicense(const License* license)