Initial GPUArrays integration

[maleadt]

For a very underwhelming demo:

julia> CLArray([1]) .+ 1
1-element CLArray{Int64, 1}:
 2

[codecov]

Codecov Report

Attention: Patch coverage is 41.07143% with 33 lines in your changes missing coverage. Please review.

Project coverage is 71.60%. Comparing base (f0c934c) to head (99f662f).
Report is 9 commits behind head on master.

Files with missing lines	Patch %	Lines
src/gpuarrays.jl	12.90%	27 Missing ⚠️
src/array.jl	76.00%	6 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #232      +/-   ##
==========================================
- Coverage   80.06%   71.60%   -8.46%     
==========================================
  Files           6        7       +1     
  Lines         316      324       +8     
==========================================
- Hits          253      232      -21     
- Misses         63       92      +29     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.