Add user agent specification support

[#80589458]
Implement tests on deserialization for all api responses

[#80589458]
Moving requests and responses into more logical formats

[#80589458]
Remove old, bad response models

[#80589458]
Remove and compile unused classes. Clean up documentation and formatting.

[#80589458]
Update HTTP client to properly handle headers

[#80589458]
fix tests to use new http client

[#80589458]
Clean up comments and useless classes.

[#80589458]
validation: be more accurate, small tweaks
add ability to shutdown client
models: fix a few missing params, etc
models: fix null issues
no more NullPointerExceptions when using models
no more sending null params to fullcontact
card reader view reqs can use access token
FCCallback is interface, logic extracted to FCRetrofitCallback
user agent: use version number
add simple toString for response models
use better rate limiting logic
minor changes to make tests pass
Merge pull request #13 from fullcontact/version2-working

final changes - Version2 working