Origin as a callable to construct OffsetArrays

[jishnub]

Based on the discussion in #274, this changes the behavior of Origin to make shifting the origin of arrays more convenient.

After this, the following work:

julia> using OffsetArrays: Origin

julia> a = [1 2; 3 4]
2×2 Matrix{Int64}:
 1  2
 3  4

julia> b = Origin(0)(a)
2×2 OffsetArray(::Matrix{Int64}, 0:1, 0:1) with eltype Int64 with indices 0:1×0:1:
 1  2
 3  4

julia> Origin(b)(a)
2×2 OffsetArray(::Matrix{Int64}, 0:1, 0:1) with eltype Int64 with indices 0:1×0:1:
 1  2
 3  4

[codecov]

Codecov Report

Merging #276 (d2905cb) into master (54ade62) will decrease coverage by 0.61%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master     #276      +/-   ##
==========================================
- Coverage   96.52%   95.90%   -0.62%     
==========================================
  Files           5        5              
  Lines         460      464       +4     
==========================================
+ Hits          444      445       +1     
- Misses         16       19       +3     

Impacted Files	Coverage Δ
src/axes.jl	100.00% <ø> (ø)
src/OffsetArrays.jl	97.77% <100.00%> (-0.63%)	⬇️
src/origin.jl	100.00% <100.00%> (ø)
src/utils.jl	96.00% <0.00%> (-2.00%)	⬇️

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[johnnychen94]

I have this in my todo list but was caught by other things. Thank you so much for handling this!

I assume you'll add test later?

[johnnychen94]

I'm so glad that we've created this useful Origin concept that saves me from the mind-twisting offset calculation trials.