add mergeDataEntries!

[dehann]

No description provided.

[codecov]

Codecov Report

Merging #906 (eeab948) into master (5cbec78) will decrease coverage by 0.14%.
The diff coverage is 52.94%.

@@            Coverage Diff             @@
##           master     #906      +/-   ##
==========================================
- Coverage   76.55%   76.41%   -0.15%     
==========================================
  Files          35       35              
  Lines        3011     3027      +16     
==========================================
+ Hits         2305     2313       +8     
- Misses        706      714       +8     

Impacted Files	Coverage Δ
src/DistributedFactorGraphs.jl	100.00% <ø> (ø)
src/DataBlobs/services/AbstractDataEntries.jl	67.21% <52.94%> (-6.13%)	⬇️

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[Affie]

I also think merge is the correct thing to do here as apposed to copy.
Just 2 things:

• I think merge should follow julia: "If the same key is present in another collection, the value for that key will be the value it has in the last collection listed"
• Please add tests