Optimize deepcopy of system

[daniel-thom]

This PR does two things related to https://github.com/NREL-SIIP/PowerSystems.jl/issues/762:

• Adds infrastructure to allow PowerSystems to perform a more efficient deepcopy. Instead of serializing and deserializing a system it can call this new function to make a copy of the HDF5 file.
• Fixes a bug that prevented verification of in-memory time series data.

[codecov[bot]]

Codecov Report

Merging #242 (49c6c7a) into master (70b6c37) will increase coverage by 0.16%. The diff coverage is 85.71%.

@@            Coverage Diff             @@
##           master     #242      +/-   ##
==========================================
+ Coverage   75.37%   75.54%   +0.16%     
==========================================
  Files          43       43              
  Lines        3123     3140      +17     
==========================================
+ Hits         2354     2372      +18     
+ Misses        769      768       -1     

Flag	Coverage Δ
unittests	75.54% <85.71%> (+0.16%)	:arrow_up:

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
src/in_memory_time_series_storage.jl	72.38% <0.00%> (ø)
src/utils/test.jl	50.00% <ø> (ø)
src/components.jl	90.07% <90.90%> (+0.07%)	:arrow_up:
src/hdf5_time_series_storage.jl	93.52% <100.00%> (+0.13%)	:arrow_up:
src/system_data.jl	86.32% <100.00%> (+0.05%)	:arrow_up:
src/utils/utils.jl	61.18% <0.00%> (-0.43%)	:arrow_down:
src/utils/lazy_dict_from_iterator.jl	96.15% <0.00%> (-0.15%)	:arrow_down:
src/utils/print.jl	37.57% <0.00%> (+0.87%)	:arrow_up:
src/InfrastructureSystems.jl	80.00% <0.00%> (+20.00%)	:arrow_up: