Use copyto! in constructors

[dlfivefifty]

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[codecov]

Codecov Report

Merging #217 (f2df693) into master (7a13ed4) will decrease coverage by 0.06%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master     #217      +/-   ##
==========================================
- Coverage   92.66%   92.60%   -0.07%     
==========================================
  Files          15       15              
  Lines        1446     1446              
==========================================
- Hits         1340     1339       -1     
- Misses        106      107       +1     

Impacted Files	Coverage Δ
src/blockarray.jl	96.11% <ø> (ø)
src/pseudo_blockarray.jl	86.72% <ø> (ø)
src/blockproduct.jl	91.37% <0.00%> (-1.73%)	⬇️

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