Add ability to disable SSL verification

[lpatino10]

This PR gives users the ability to disable SSL verification in subsequent HTTP requests. The new way to set this also includes setting a proxy, and this is all wrapped up in a new HttpConfigOptions class.

Documentation has been added to the main README to explain this to users.

[codecov-io]

Codecov Report

Merging #989 into codegen-updates will increase coverage by 0.11%.
The diff coverage is 34.14%.

@@                  Coverage Diff                  @@
##             codegen-updates     #989      +/-   ##
=====================================================
+ Coverage              41.37%   41.49%   +0.11%     
- Complexity              1851     1877      +26     
=====================================================
  Files                    672      673       +1     
  Lines                  16223    16333     +110     
  Branches                 907      913       +6     
=====================================================
+ Hits                    6713     6778      +65     
- Misses                  9138     9183      +45     
  Partials                 372      372

Impacted Files	Coverage Δ	Complexity Δ
.../watson/developer_cloud/service/WatsonService.java	46.87% <0%> (-0.5%)	36 <0> (ø)
...watson/developer_cloud/http/HttpConfigOptions.java	100% <100%> (ø)	3 <3> (?)
...tson/developer_cloud/http/HttpClientSingleton.java	52% <7.4%> (-25.09%)	9 <0> (ø)
...developer_cloud/assistant/v1/model/OutputData.java	47.82% <0%> (-9.87%)	10% <0%> (+5%)
...eveloper_cloud/speech_to_text/v1/SpeechToText.java	75% <0%> (ø)	51% <0%> (+4%)	⬆️
...cloud/speech_to_text/v1/model/GetAudioOptions.java	64% <0%> (+1.5%)	4% <0%> (+1%)	⬆️
...d/speech_to_text/v1/model/DeleteCorpusOptions.java	64% <0%> (+1.5%)	4% <0%> (+1%)	⬆️
...loud/speech_to_text/v1/model/GetCorpusOptions.java	64% <0%> (+1.5%)	4% <0%> (+1%)	⬆️
...ud/speech_to_text/v1/model/DeleteAudioOptions.java	64% <0%> (+1.5%)	4% <0%> (+1%)	⬆️
... and 3 more

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[mediumTaj]

👍 looks good!