Integrate and use the Dom Model

The DOM model has two primary uses cases:

1. it will be used in the LSP's code model 
2. it acts an an interface for Qt Design Studio to modify QML files via a high level API

On a high level, the remaining tasks are

There are various parts to this
1. integrate the Dom model in Qt (done in 6.3)
2. Integrate and use it in Qml designer
3. Use it in the  LSP
4. Document it