Better error message with Missings

[VEZY]

When we pass a DataFrame to Weather (or TimeStepTable{Atmosphhere}) that has some missing values, we get the following error:

julia> w = Weather(df)
ERROR: MethodError: no method matching var"#Atmosphere#3"(::Missing, ::Float64, ::Missing, ::Missing, [...])

This is because we don't accept Missing values for the default Atmosphere variables (and this is the right way to do so).

But, we could print a nicer error message because it is complicated to understand where the error comes from with this one.

We could have something like:

ERROR: ArgumentError: Missing values found in the DataFrame. This is not authorized.

[VEZY]

Fixed in 19f61c3 and 9beda3b