Subo descarga de imagen desde el repositorio funcionando.
Incluye condiciones de error.

 On branch issue_34
 Changes to be committed:

	modified:   database/ImageRepositoryDB.sql
	modified:   testing/virtualMachineServerTester.py
	modified:   virtualMachineServer/networking/packets.py
	modified:   virtualMachineServer/reactor/vmServerReactor.py
	modified:   virtualMachineServer/threads/fileTransferThread.py