plugins/ola: OlaClient api has changed. sendDMX() is async now.

OlaClient::sendDMX has a different signature as old sendDmx.
It takes now an callback as additional argument and return value
is void.
ui/palettegenerator: fix missing include <QObject>
ui/test: fix shadow/out-of-tree builds

all ui/tests include headers which includes generated headers from
ui files. These generated headers couldn't found, because the output
directory wasn't added to it's include directory.
Merge https://github.com/lynxis/qlcplus