How to build/ update a new assistant.qch for Assistant internal help

- update:
    - open assistant.qdocconf, update year and qt version

    - ..\..\..\..\qdoc3\debug\qdoc3.exe assistant.qdocconf
        will generate an folder html containing all required stuff

    - cp assistant.qhp to generated html folder
    - run qhelpgenerator html\assistant.qhp -o ..\assistant.qch

    - rebuild assistant

- to test your changes:
    - remove assistant.qch in your cache directory
    - restart assistant
