QML plugins are redundant

We currently provide largely empty plugins for many of our QML modules, simply to link the resepective libraries at runtime rather than at compile time. In particular we have:

• QtQml and qmlplugin
• QtQuick and qtquick2plugin
• QtQmlModels and modelsplugin
• QtQmlWorkerScript and workerscriptplugin
• QtQuickTest and qmltestplugin
• QtQuickShapes and qmlshapesplugin
• QtQuickParticles and particlesplugin

The duplication is pure overhead. Also, by requiring the plugins to drive the library initialization, we run into linking problems: As the empty plugins don't reference any symbols from the libraries, the linker tends to "optimize" the type registrations or even the whole dependency out. Several hacks have been introduced to avoid this.

Instead of loading those plugins at runtime, the target application could just link the respective modules at compile time. The QML engine could detect that the types are already available and skip the plugin loading.

As a second step, the plugins in question, when loaded, could advise the user via a warning to link the library instead.