RemoteRunner: worker startup scripts

RemoteRunner workers may be given one more scripts to execute on startup by adding an extension method to the worker with the <gtWorkerStartupScript> pragma, e.g.:

The script must be added to each worker class in which it is to be executed, i.e. scripts added to GtRrWorker Object << #GtRrWorker slots: { #uid . #attributes . #connectionStrategy . #resultQueue . #lastHeartbeat . #heartbeatProcess . #heartbeatDelay . #stopFlag . #executionContext . #readProcess . #exceptionHandlingStrategy . #logger }; tag: 'Worker'; package: 'RemoteRunner' will not be executed in GtRrInImageWorker GtRrWorker << #GtRrInImageWorker slots: { #remoteRunner . #connection }; tag: 'Worker'; package: 'RemoteRunner' and visa-versa.