CamelCasePropertyNamesContractResolver causes incompatibility with Spec

[deinok]

ref: http://facebook.github.io/graphql/June2018/#sec-Names
ref: #58

However, using CamelCasePropertyNamesContractResolver on the entire
payload, also changes data field names to camelCase. Data fields (per
spec) can be any desired casing, so the current graphql-client library
won't work where data field names are not camel case.

So, the idea is force Query, OperationName and Variables to CamelCase without forcing the usage CamelCasePropertyNamesContractResolver that causes that the model of Variables to be forced to be CamelCase.

This needs further investigation, like:

• Requests: It causes renaming of variables?
• Response: Is the response also afected by this?
• Serialization: Is there a way to fix this issues without depending on JSON implementation? Other Serialization formats cases

CC: @sys-dev