reexport commonly used array/view packages

[johnnychen94]

Four packages are reexported by ImageCore:

• IndirectArrays
• MappedArrays
• OffsetArrays
• TiledIteration

The extra time overhead seems good to me. (Although in static compiled languages like C++ there's so-called best practice -- "what you don’t use, you don’t pay for", in Julia we still don't have a good solution for this, hence we need to make a tradeoff between the maintenance and overhead)

@time using ImageCore
# PR: 0.631698 seconds (1.17 M allocations: 86.323 MiB, 7.37% gc time, 0.52% compilation time)
# master: 0.565541 seconds (1.16 M allocations: 85.314 MiB, 6.02% gc time, 0.62% compilation time)

[codecov]

Codecov Report

Merging #164 (34ea3d6) into master (5b2202d) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #164   +/-   ##
=======================================
  Coverage   66.42%   66.42%           
=======================================
  Files          10       10           
  Lines         563      563           
=======================================
  Hits          374      374           
  Misses        189      189           

Impacted Files	Coverage Δ
src/ImageCore.jl	71.42% <ø> (ø)

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[johnnychen94]

Since ColorVectorSpace 0.9 brings many new symbols, we might also want to reexport that, too.

[timholy]

FWIW I'm fine with this change if you want it (I haven't checked the costs myself).