Update github.com/opencontainers/runtime-tools to v0.6.0

Also add new dependencies on github.com/xeipuuv/gojson* (brought up by
new runtime-tools) and adapt the containerd/cri code to replace the APIs
that were removed by runtime-tools.

In particular, add new helpers to handle the capabilities, since
runtime-tools now split them into separate sets of functions for each
capability set.

Replace g.Spec() with g.Config since g.Spec() has been deprecated in the
runtime-tools API.

Signed-off-by: Filipe Brandenburger <filbranden@google.com>

vendor/github.com/xeipuuv/gojsonreference/README.md

@@ -0,0 +1,10 @@
+# gojsonreference
+An implementation of JSON Reference - Go language
+
+## Dependencies
+https://github.com/xeipuuv/gojsonpointer
+
+## References
+http://tools.ietf.org/html/draft-ietf-appsawg-json-pointer-07
+
+http://tools.ietf.org/html/draft-pbryan-zyp-json-ref-03