Add access to plasma model properties

[Mateasek]

Currently PlasmaModel attributes are not accessible from python. Making some of them accessible would provide an easier way of investigating and understanding results provided by cherab. I think in general it would increase the usefulness of the plasma object and sometimes save a lot of time. For example reaction rates could be obtained from the plasma object instead of the need to construct them manually. This could be also useful for debugging of simulations. I propose adding getters to:

ExcitationLine, ExcitationLine:

• _line
• _wavelength
• _rates

TotalRadiatedPower:

• _element
• _charge
• _plt_rate
• _prb_rate

Are there any more objections to this idea? There can be a reason for the current state which I missed. Also are there any more ideas which could be connected to this change?

[jacklovell]

I don't see any harm in doing this. You should ensure that the documentation is updated too, to include these properties.