General discussion about the new QML API

[bnogalm]

The plan is to build an optional higher level API to interact with horizon from QML.
Using a new .pri subproject, the plan is to add a defined "QML_STELLAR_API" to conditional compile Q_DECLARE_METATYPE/qmlRegisterType/interface classes etc.. as required.

I realized that the below classes could be nice to have in any Stellar application and would be great to implement a QML declarative version of them:

• StellarConfiguration, singleton to setup common settings (use public or test network, horizon server, etc.. ) and to access Stellar current variables. API version number, minimal fee, base reserve, etc...
• FederationResolver, class to resolve federations
• QQuickImageProvider to resolve assets icons. URI could be something like stellar://icon?issuer=issuer_public_key&code=asset_code
• Repeater/Loader like requests classes. For each request class, a declarative version to request data to horizon.

You can feel free to comment them or suggest some more ideas.