Added conformance test impl file to CMake.

Fixes JSON Loading of Any messages with Unknown Fields  in C++

Added cmake build files for the conformance test runner.

Add contributing guidelines.

* Fix well known type class not inheriting Message

Previously, well known types only implement Message interface but not inhert it.
Fix the problem by calling zend_do_inheritance

* Add back commented tests

* Add missing reference to conformanc_test_impl.cc in Makefile

* Update conformance failure list

Credit goes to @mercret for the fix.

Use ./tests.sh cpp to run it

update version

Request new option extension (and update URLs for existing projects)

Update options.md | fix website url for C# port

Update my projects' (DCCL / Goby) URLs.
Propose new extension for CGSN Mooring project.

I want to use the conformance tests from upb, which is switching
to CMake.

Update options.md | fix website url for C# port of protocol buffers.. From `http://github.com/jskeet/dotnet-protobufs` to `https://github.com/jskeet/protobuf-csharp-port`

Revert changed links in Dockerfiles.

These changes require building new docker images and without new images
our kokoro tests are all failing.

Replace repo links.

Related to #658 and #5007.

Fix TryCreateParentDirectory on Windows

Change deprecated Bazel single file attr param

This removes the need for --incompatible_disable_deprecated_attr_params
when using Protobuf

* _SURROGATE_PATTERN check for ucs4
Skip some test for ucs2 by sys.maxunicode

Document wrapper non-uses

Document the cases where the wrapper well-known types are not useful.

Fix issues discovered in up-integration.

Add status badge for bazel build.

Fix bazel test.

* Fixes https://github.com/google/protobuf/issues/5031
* Fixes https://github.com/google/protobuf/issues/5037

Down-integrate proto2 namespace fix.

Fix json parsing of wrapper values