kron for AbstractFill

[jishnub]

After this,

julia> f = Fill(3, 2, 4)
2×4 Fill{Int64}, with entries equal to 3

julia> kron(f, f)
4×16 Fill{Int64}, with entries equal to 9

julia> g = Zeros(2)
2-element Zeros{Float64}

julia> kron(g, g)
4-element Zeros{Float64}

julia> E = Eye(4)
4×4 Eye{Float64}

julia> kron(E, E)
16×16 Eye{Float64}

[codecov]

Codecov Report

Merging #268 (14a0423) into master (655c089) will increase coverage by 99.75%.
The diff coverage is 100.00%.

@@             Coverage Diff             @@
##           master     #268       +/-   ##
===========================================
+ Coverage    0.00%   99.75%   +99.75%     
===========================================
  Files           5        5               
  Lines         814      828       +14     
===========================================
+ Hits            0      826      +826     
+ Misses        814        2      -812     

Impacted Files	Coverage Δ
src/FillArrays.jl	99.42% <ø> (+99.42%)	⬆️
src/fillalgebra.jl	100.00% <100.00%> (+100.00%)	⬆️

... and 3 files with indirect coverage changes

📣 We’re building smart automated test selection to slash your CI/CD build times. Learn more