Fix show for BlockRange

[jishnub]

On master

julia> show(BlockRange((1:3, 1:3)))
BlockRange(1:31:3)

There is a missing comma between the ranges. After this PR,

julia> show(BlockRange((1:3, 1:3)))
BlockRange(1:3, 1:3)

This also changes the "text/plain" display of a BlockRange to make it easier to understand.
On master

julia> BlockRange((1:3, 1:3))
3×3 BlockRange{2, Tuple{UnitRange{Int64}, UnitRange{Int64}}}:
 Block(1, 1)  Block(1, 2)  Block(1, 3)
 Block(2, 1)  Block(2, 2)  Block(2, 3)
 Block(3, 1)  Block(3, 2)  Block(3, 3)

This PR uses forwards it to the default show:

julia> BlockRange((1:3, 1:3))
BlockRange(1:3, 1:3)

This matches the display for CartesianIndices:

julia> CartesianIndices((1:3, 1:3))
CartesianIndices((1:3, 1:3))

[codecov]

Codecov Report

Merging #280 (eea492a) into master (b03703f) will increase coverage by 91.99%.
The diff coverage is 100.00%.

@@             Coverage Diff             @@
##           master     #280       +/-   ##
===========================================
+ Coverage    0.00%   91.99%   +91.99%     
===========================================
  Files          16       16               
  Lines        1462     1474       +12     
===========================================
+ Hits            0     1356     +1356     
+ Misses       1462      118     -1344     

Impacted Files	Coverage Δ
src/blockaxis.jl	96.26% <ø> (+96.26%)	⬆️
src/blockindices.jl	83.06% <ø> (+83.06%)	⬆️
src/blocklinalg.jl	94.44% <ø> (+94.44%)	⬆️
src/show.jl	100.00% <100.00%> (+100.00%)	⬆️

... and 12 files with indirect coverage changes

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