libtorc-qml: Move OMX code into libtorc-qml
libtorc-core: Add 2 new USB events
libtorc-core: Support deviced added/removed events in TorcUSB
libtorc-core: Use a TorcEvent to signal USB events on OSX

- this ensures the notifications are received in the correct thread and
avoids the need to move any QObjects into the correct thread later.
libtorc-qml: Simplify TorcCECDevice creation

- now that USB notifications are received in the correct thread on all
platforms, we don't need to go through the hoops of moving threads.
libtorc-core: Remove certain TorcAdminThread functionality