libtorc-qml: Track video timestamp and framerate in TorcSGVideoPlayer
libtorc-core: Convert action handling to event handling.

- event handling is more flexible:)
libtorc-core: Fix TorcDecoder::HandleEvent documentation.
libtorc-core: More action to event conversions
libtorc-core: Fix typo in TorcPlayer
libtorc-qml: Fix mouse to video translation.
libtorc-qml: Generalise event handling in TorcSGVideoPlayer
libtorc-qml: Stub out wheel event handling