Fix p-norm for unitful quantities

[JoshuaLampert]

This is #1125 and #1128 for general p-norms, where $p\neq 0,2,\infty$. Before:

julia> norm(SVector(1.0, 2.0)*u"m", 1)
ERROR: DimensionError: 0.0 and 3.0 m are not dimensionally compatible.
Stacktrace:
 [1] _lt
   @ ~/.julia/packages/Unitful/dHMk1/src/quantities.jl:250 [inlined]
 [2] <(x::Quantity{Float64, NoDims, Unitful.FreeUnits{…}}, y::Quantity{Float64, 𝐋, Unitful.FreeUnits{…}})
   @ Unitful ~/.julia/packages/Unitful/dHMk1/src/quantities.jl:240
 [3] <(x::Int64, y::Quantity{Float64, 𝐋, Unitful.FreeUnits{(m,), 𝐋, nothing}})
   @ Unitful ~/.julia/packages/Unitful/dHMk1/src/quantities.jl:242
 [4] macro expansion
   @ ~/.julia/dev/StaticArrays/src/linalg.jl:331 [inlined]
 [5] _norm
   @ ~/.julia/dev/StaticArrays/src/linalg.jl:311 [inlined]
 [6] norm(a::SVector{2, Quantity{Float64, 𝐋, Unitful.FreeUnits{(m,), 𝐋, nothing}}}, p::Int64)
   @ StaticArrays ~/.julia/dev/StaticArrays/src/linalg.jl:310
 [7] top-level scope
   @ REPL[27]:1
Some type information was truncated. Use `show(err)` to see complete types.

and

julia> norm(SVector(0.0, 0.0)*u"nm", 1)
NaN nm

After this PR:

julia> norm(SVector(1.0, 2.0)*u"m", 1)
3.0 m

and

julia> norm(SVector(0.0, 0.0)*u"nm", 1)
0.0 nm

[mateuszbaran]

Thanks, LGTM. Could you just bump patch version?

[JoshuaLampert]

Thanks, LGTM. Could you just bump patch version?

Done in 2a717dc.