Remove the C#-specific field_presence_test.proto, using unittest_no_field_presence.proto instead.

This is the start of establishing a C# namespace of "Google.ProtocolBuffers.TestProtos.Proto3" for proto3-syntax protos.
We could optionally split the directory structure as well into Proto2 and Proto3 for clarity.

C# generate_proto.sh and buildall.sh scripts

C# cleanup

Dockerfile for building protoc on Centos 6.6

Fixes for Mono

Uncomment conflict fields from pkg-config files.

Convert back to using NUnit, which is now loaded via NuGet.

The referenced bug was fixed in 2007 and has been released in pkg-config-0.23
(16.Jan.2008). The fixed version is widely available.

This includes the NUnit test adapter which allows NUnit tests to be run under VS without any extra plugins.
Unfortunate the compatibility tests using the abstract test fixture class show up as "external" tests, and aren't well presented - but they do run.

Performance optimization for small messages without unknown fields

adding globals() to exec call for python3 compatibility

Handle 0-length byte buffers in micro and nano protobufs

Fix java compilation issues when processing large .proto files

Add C# namespace to .proto files (e.g. descriptors, unit tests)

Run conformance tests against Java for the Travis build.

Change-Id: I8ef8664f7facf86028be3f4f0d5d2efc8a685d6d

Objective C compiler plugin and runtime

Cleanup setup.py