Bring to master the ObjC documentation changes made for the release.

Make xctool work on the release branch too.

This will hopefully make xctool work on Travis too (cross fingers!)

Add npm, gem and cocoapods badges

Added some file-level comments to Node source files

Add nuget pkg version badge for C#

Bazel like output

Fix for long-running tsan test

Travis for iOS

Split tests into one scheme per test case

Fix RouteGuide example to use the last surface

Prevent XCode 7 from showing spurious warnings

Device builds require code signing, that isn’t set up (they probably
wouldn’t work anyway - I don’t think Travis is attaching devices to
their VMs).

For local running one can still tests AllTests, but for C.I. one can
test the 4 of them in parallel (and, importantly, deactivate the remote
interop tests until we fix them on Travis; while keeping the rest).

I had to make the remote tests a subclass of an abstract InteropTests
(like InteropTestsLocalSSL and InteropTestsLocalCleartext), and then
deactivate the abstract InteropTests on the 4 schemes that use it.

Eventually all samples will be tested.

Add OpenCover coverage for C#

Fixing 'all' run tests target.

This will hopefully make xctool work on Travis too (cross fingers!)