Cleaner dispatching onto StaticArrays

[apkille]

As discussed in the docs, creating Gabs types that wrap around static arrays requires the user to specify the array size. This isn't really necessary, as the array size is implicit in the choice of symplectic basis. So, there should be a more straightforward way of doing this from the high-level interface. Rather than, for example,

vacuumstate(SVector{4}, SMatrix{4,4}, QuadBlockBasis(2)) -> GaussianState{QuadBlockBasis{Int64}, SVector{4, Float64}, SMatrix{4, 4, Float64, 16}}

a user should be able to simply write

vacuumstate(SVector, SMatrix, QuadBlockBasis(2)) -> GaussianState{QuadBlockBasis{Int64}, SVector{4, Float64}, SMatrix{4, 4, Float64, 16}}

where manually entering array dimension information is not required.