Constructor should check that dimension and units are consistent

Right now, one can create a quantity that has units `s` (seconds, a time unit) but dimension `𝐋` (length) by just calling the constructor with those type parameters:
```julia
julia> using Unitful: Quantity, 𝐋, s

julia> x = Quantity{Int64, 𝐋, typeof(s)}(2)
2 s

julia> unit(x)
s

julia> dimension(x)
𝐋

julia> x isa Unitful.Length
true

julia> x isa Unitful.Time
false

julia> unit(x) isa Unitful.LengthUnits
false

julia> unit(x) isa Unitful.TimeUnits
true
```

Start by reproducing the Quantity constructor example from the issue and inspect the constructor's handling of its dimension and unit type parameters. Done means inconsistent parameters such as length with seconds are rejected, while consistent quantities remain constructible.

Written by the indexing model from the issue text.