Add json method for pack serialization/deserialization

[mylibrar]

This PR is the first step towards fixing #836.

Description of changes

Serialize/deserialize pack into/from json data.

Possible influences of this PR.

Remove dependency on pickle and jsonpickle in pack deserilization/serialization.

Test Conducted

entry_data_structures_test.py
multi_pack_test.py
entry_data_structures_test.py

[codecov]

Codecov Report

Merging #917 (68e1080) into master (5f43e72) will increase coverage by 0.06%.
The diff coverage is 94.44%.

@@            Coverage Diff             @@
##           master     #917      +/-   ##
==========================================
+ Coverage   80.99%   81.06%   +0.06%     
==========================================
  Files         256      256              
  Lines       19821    19851      +30     
==========================================
+ Hits        16055    16093      +38     
+ Misses       3766     3758       -8     

Impacted Files	Coverage Δ
forte/data/data_pack.py	85.00% <ø> (ø)
...atasets/wikipedia/dbpedia/dbpedia_datasets_test.py	100.00% <ø> (ø)
forte/processors/base/writers.py	68.60% <50.00%> (ø)
forte/data/base_pack.py	77.77% <92.59%> (+0.80%)	⬆️
forte/common/constants.py	100.00% <100.00%> (ø)
forte/data/container.py	80.48% <100.00%> (+4.01%)	⬆️
forte/data/multi_pack.py	83.14% <100.00%> (+0.12%)	⬆️
forte/data/ontology/top.py	79.30% <100.00%> (+0.05%)	⬆️
tests/forte/data/entry_data_structures_test.py	90.25% <100.00%> (+4.39%)	⬆️
tests/forte/data/multi_pack_test.py	97.13% <100.00%> (+0.07%)	⬆️
... and 1 more

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[hunterhector]

Can we add something serialization example (the actual json file) in the example folder: https://github.com/asyml/forte/tree/master/examples/serialization