JSON DOM refactor (dotnet/corefx#41041)

JSON DOM refactor (dotnet/corefx#41041)

* work on review comments, documentation changes included

* work on including review comments

* work on including review comments

* StringComparison methods improvements

* work on adressing review comments

* helping comment added

* StringComparison tests improved to check all enum values

* setting CurrentCulture test added

* review comments included

* build fixes

* CurrentCulture test removed

* Address nits and react to recent API changes.

Commit migrated from https://github.com/dotnet/corefx/commit/a0f71fa14ecd17c6aee146b8ef76aaec0dd389ed