* Use latest pylint in Python 3.7 (they dropped support for PY2)
* Make latest pylint happy
* Forced to upgrade to shellcheck 0.4.4
* Make shellcheck 0.4.4 happy
* Adopt reviewers' advice to reduce global disabled rules
using ccache when building under a docker image isn't useful when
building on kokoro as each build runs on a fresh VM.
Originally ccache builds were used to speed up jenkins builds,
now removing to guarantee build isolation and simplify stuff.
Features included in this merge:
- Added script to build and upload docker image for matrix test.
- Added script to create test cases and created go__master testcases based on it.
- Created dictionary for runtimes and gRPC releases for supported languages.
- Added go 1.7 and 1.8 Dockerfile/templates.
See tools/interop_matrix/README.md for details.
-) created a .profile at the root of the docker image - seems the new nvm script requires that.
-) installing simplejson and mako python packages, for the sanity check.
-) calling prepare_travis.sh in order to try and download precompiled packages for openssl and protobuf.
-) using the new "config" axis.
-) improved the output of prepare_travis.sh.