.executemany doesn't use Connection.executemany

[twall]

The executemany method of SqlliteMultiThread just repeatedly calls its own execute, queuing individual execute calls.

It should be straightforward to push an "executemany" op onto the thread and call executemany on those requests.

[twall]

Sample implementation:

                    try:
                        if req == '--many--':
                            cursor.executemany(arg[0], arg[1])
                        else:
                            cursor.execute(req, arg)
                    except Exception as err:

with a corresponding executemany definition:

        def executemany(self, req, items):
            self.execute('--many--', (req, items))