This is a specialized subclass of AbstractEffectLoader to load binary
effect plugins. It used the KPluginTrader to find all candidates to load.
The loader is able to detect incorrect ABI versions through the
pluginVersion() and uses the methods exposed by the new
KWin::EffectPluginFactory to check whether the Effect is supported and
should be enabled by default.
The unit test for this loader comes with two plugins: one is able to be
loaded and provides a supported and enabledByDefault method which can be
tweaked during the test to get all the conditions we want to test for.
The second plugin uses an incorrect plugin version and thus cannot get
loaded.
