Proto commits in google/GTXiLib

These 3 commits are when the Protocol Buffers files have changed:

Commit:7379908
Author:CooperCorona

Replace Protobuf dependency with pure C++ data models.

The documentation is generated from this commit.

Commit:20d99f2
Author:CooperCorona

Add Obj-C++ tests for C++ classes. Add translations and classes to retrieve them. Add data structures for C++ check results and displaying messages about results to users.

Commit:409c037
Author:sidj

Added support for XCUITests (with a subset of checks). Add check for dynamic text check. Fixed typos and some APIs have been renamed for clarity. APIs imporvements: more flexible scan APIs that return result info. Improved accessibility auto enable code. Extracted GTX core logic into a C++ library and used Protobuf for cross platform execution.