Add dimension separator as a type parameter

[mkitti]

This replaces #150 by implementing the dimension_separator as a type
parameter.

I also intend to add Zarr specification version as a type parameter in forthcoming commits.

[mkitti]

cc: @bjarthur @StephanPreibisch

[coveralls]

Pull Request Test Coverage Report for Build 14183287381

Details

• 67 of 100 (67.0%) changed or added relevant lines in 5 files are covered.
• 3 unchanged lines in 2 files lost coverage.
• Overall coverage decreased (-1.6%) to 84.413%

---

Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
src/metadata.jl	10	12	83.33%
src/Storage/http.jl	8	11	72.73%
src/ZArray.jl	6	9	66.67%
src/ZGroup.jl	15	18	83.33%
src/Storage/versionedstore.jl	28	50	56.0%

Files with Coverage Reduction	New Missed Lines	%
src/ZGroup.jl	1	81.32%
src/Storage/Storage.jl	2	75.64%

Totals
Change from base Build 13680422725:	-1.6%
Covered Lines:	964
Relevant Lines:	1142

---

💛 - Coveralls

[mkitti]

@bjarthur I believe the dimension separator of / is now working with Zarr v2.

julia> using Zarr

julia> readdir("ts_test/zarr_v2_raw")
9-element Vector{String}:
 ".zarray"
 "0"
 "1"
 "2"
 "3"
 "4"
 "5"
 "6"
 "7"

julia> read("ts_test/zarr_v2_raw/.zarray", String) |> print
{"chunks":[8,8,8],"compressor":null,"dimension_separator":"/","dtype":"<f8","fill_value":null,"filters":null,"order":"C","shape":[64,64,64],"zarr_format":2}
julia> g = zopen("ts_test")
ZarrGroup at DirectoryStore{2, '/'}("ts_test") and path 
Variables: zarr_v2_raw 

julia> typeof(g)
ZGroup{DirectoryStore{2, '/'}}

julia> arr = g["zarr_v2_raw"]
ZArray{Float64} of size 64 x 64 x 64

julia> typeof(arr)
ZArray{Float64, 3, Zarr.NoCompressor, DirectoryStore{2, '/'}}

julia> arr[1:10,1,1]
10-element Vector{Float64}:
 0.5031057549501186
 0.30753242290354865
 0.7604873102093034
 0.3274341519944033
 0.016695504839365882
 0.4110998920786101
 0.2731260969810403
 0.5038009325254829
 0.1788864699667917
 0.8449113642679142

[mkitti]

I have prototyped Zarr v3 on top of this and #180
https://github.com/mkitti/Zarr.jl/tree/mkitti-v3-prototype