added a signal handler to remove GCM messages from the queue when a GCMMessage object is deleted
added a signal handler to remove GCM messages from the queue when a GCMMessage object is deleted

tndatacommons/tndata_backend,tndatacommons/tndata_backend,izzyalonso/tndata_backend,izzyalonso/tndata_backend,tndatacommons/tndata_backend,izzyalonso/tndata_backend,izzyalonso/tndata_backend,tndatacommons/tndata_backend