Optimize storage of time series

[daniel-thom]

This makes two changes:

1. Add option to compress time series data.
2. Change how shared time series references are stored. The earlier method caused stranded space.

These changes required the addition of a format version so that we can maintain backwards compatibility with existing datasets.

I also added some documentation. I added a description of the time series HDF5 format. I also added descriptor rules for our auto-generation code since more people are using that feature.

Regarding compression, I'm thinking that we can expose this with kwargs to the System constructor. We could provide a simple enable_compression as well as compression that take the CompressionSettings struct defined here.

[codecov[bot]]

Codecov Report

Merging #227 (b39a127) into master (af9e9f9) will increase coverage by 0.08%. The diff coverage is 89.83%.

@@            Coverage Diff             @@
##           master     #227      +/-   ##
==========================================
+ Coverage   75.01%   75.10%   +0.08%     
==========================================
  Files          43       43              
  Lines        3054     3073      +19     
==========================================
+ Hits         2291     2308      +17     
- Misses        763      765       +2     

Flag	Coverage Δ
unittests	75.10% <89.83%> (+0.08%)	:arrow_up:

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

Impacted Files	Coverage Δ
src/time_series_storage.jl	77.77% <80.00%> (+2.77%)	:arrow_up:
src/hdf5_time_series_storage.jl	93.37% <90.38%> (-0.61%)	:arrow_down:
src/in_memory_time_series_storage.jl	71.84% <100.00%> (+0.27%)	:arrow_up:
src/system_data.jl	86.26% <100.00%> (+0.05%)	:arrow_up:
src/utils/lazy_dict_from_iterator.jl	96.15% <0.00%> (-0.15%)	:arrow_down:
src/utils/utils.jl	61.18% <0.00%> (+0.42%)	:arrow_up:

[jd-lara]

Regarding compression, I'm thinking that we can expose this with kwargs to the System constructor. We could provide a simple enable_compression as well as compression that take the CompressionSettings struct defined here.

Agreed