Finalize QML object-creation compiler prototype

The current POC has to be finalized at some point. Finalized state means that there's little left to do on the prototype code and know-how for QML -> C++ compilation is built. For instance:

• which QML language features are supported and what is rejected (if anything)
• how QML features map to C++
• how QML compiler is intergrated with existing runtime system (e.g. QQmlEngine)
• which changes have to be done in the shared codebase (e.g. in QQmlJSScope, QQmlJSImporter, qmllint)
• how an architecture of the compiler could (should) look like

As byproduct the following things will likely be present:

• unit tests that cover compiler generated classes - gives guarantees of feature completeness/correctness
• (basic) benchmark - gives understanding of benefits of using the compiler
• converted QML example (ideally) - proves that a "real-world" application could be built with the technology (even if it's POC)