Support reading of arbitrary fields

[oruebel]

This PR is to prepare for #130

• Changed the getGroupObjects method to getStorageObjects to allow for more general lookup of groups, datasets, and attributes. The current method is limited to look-up of groups within a group. The updated getStorageObjects now supports: 1) lookup starting from datasets and groups and 2) retrieval of groups, datasets, and attributes, 3) allows the user to specify what types of storage objects to retrieve.
• Fixed an issue in the findTypes function, which previously only looked at Groups so typed objects that were datasets (e.g., VectorData) would have been ignored.
• Added unit tests for findTypes and missing tests for RegisteredType and HDF5IO
• Added new RegisteredType::readField function for reading arbitrary dataset and attribute fields
• Added second variant of the RegisteredType::readField method to allow reading of arbitrary fields that are itself instances of RegisteredType, such as, reading VectorData from a DynamicTable or reading ElectricalSeries from an NWBFile

Fix #133
Fix #131

[oruebel]

@stephprince sorry in case this caused confusion, but I needed the changes from #139 here for testing, and since #139 was not merged yet I combined it with this PR so I could run the tests. This PR is now ready for review.

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 98.64865% with 4 lines in your changes missing coverage. Please review.

Project coverage is 92.96%. Comparing base (d76f8b7) to head (1a713e0).

Files with missing lines	Patch %	Lines
src/nwb/NWBFile.cpp	50.00%	2 Missing ⚠️
tests/testRegisteredType.cpp	97.43%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #142      +/-   ##
==========================================
+ Coverage   92.01%   92.96%   +0.94%     
==========================================
  Files          61       62       +1     
  Lines        4009     4278     +269     
  Branches      262      266       +4     
==========================================
+ Hits         3689     3977     +288     
+ Misses        310      291      -19     
  Partials       10       10              

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[stephprince]

Looks good to me! Added some minor suggestions.

[oruebel]

@stephprince can you please re-approve. I committed your suggestions and added the test case you had suggested in 19fecb4