Resolve "Change the noise parametrization"

Closes #33

• Convert noise generation functions to noise objects (camel-cased identical names)
• Parametrize noises explicitly with noise generators or already-generated time series (arrays) in Instrument; default noise shapes are now explicit in the signature of the initialization function Instrument.__init__()
• Update documentation for Instrument's noises
• Add a new method generated() for ForEachObject instances that hold noise generators