Variables: solar_system, solar_kw

[zenourn]

At least one user has a solar system so when charging during daylight hours isn't necessarily feeding from the grid.

There is a question in signup survey asking if they have solar and about their setup. So if they have solar we should know and should also know the size of the system. I'm going to have to do some regex as currently just textual and will start a separate table for car-level predictors that I'm sure we'll have more of. For now will be (id, solar_system, solar_kw).