Default noise models for devices

[madagra]

Currently, the noise model parameters must be chosen to the user according to the available options. However, there is not predefined noise model associated with the available devices, even though the parameters are known.

The proposal is to define some default noise models for the available predefined devices (Chadoq2, AnalogDevice, IroiseMVP) and allow the user to select them if they want to do a noisy simulation.

The proposal comprises the following points:

• define a noise model for each device using the parameters available in the Qutip emulator backend (the only one currently supporting noise)
• include the noise model directly in to the device class
• introduce a flag to turn on and off the noise for the device in case that the backend supports it
• add the noise model to the serialization schema