Cache of compiled QML is saved in our sources folders

With Qt5.8, there is a cache of compiled QML files, it's a great feature, but having the qmlc files in the same folder of our regular qml files can cause some troubles.

The first issue is that we simply risk to add qmlc files to our svn, and we prefer keep our resources folders tree clean.
The second one is that we scan our resources folders to do hot reloading of the GUI, and having files that are always changing make our application reloading the GUI in an infinite loop.

In my opinion qmlc fies should by saved in a temporary folder that is granted to be writable in all platforms.