Use the correct include file here.
Split script engine debugger plugin into probe and UI part.
Split widget inspector plugin into probe and UI part.
Get rid of the helper class for hybrid plugins.
Abstract the way we read plugin metadata.

This is a step towards also supporting Qt5-style embedded JSON meta data.
We need this as we can't install .desktop files on Android on non-rooted
devices into the same location as the plugins.
Discard plugins with invalid meta data.