Qt Creator should include qmldir configure file for project search indeces

C++ import plugins exposed in QML need to define a file called qmldir for the plugin loading mechanism to work, but currently Qt Creator has no knowledge of this file and does not include it in the search index. This file should be included in the index, so that for example searching and replacing plugin names will also cause the plugin target mentioned in qmldir file to be renamed. A qmldir file may not be trivial to locate though, so take this task as a suggestion than something that should necessarily be fixed.