logic: multithreaded parsing

* modified the TaskParseCxx to be able to run multiple times in parallel
* made FileRegister threadsafe and changed a lot of its mechanisms
* added TaskGroupParallel that runs all children in parallel
* added TaskParseWrapper that acts as a decorator to execute some code before and after parsing.
* implemented task setup in project with 4 parsing threads
* removed SimpleTask as it was only used as interface for the LambdaTask

src/lib_parser/data/parser/cxx/ASTVisitor.cpp

@@ -1503,7 +1503,7 @@ bool ASTVisitor::isLocatedInUnparsedProjectFile(clang::SourceLocation loc)
 			{
                 std::string fileName = fileEntry->getName();
                 FilePath filePath = FilePath(fileName).canonical();
-				ret = m_fileRegister->includeFileIsParsing(filePath.str());
+				ret = m_fileRegister->includeFileIsParsed(filePath.str());
 			}
 		}
 		m_inUnparsedProjectFileMap[fileId] = ret;