Environment Specs so far had only an image URL to specify a container image.
This was fine for public images but fell short in a few of cases:
(a) Using private image registries
(b) Specifying environment variables (this is needed for workflows helm install)
(c) Setting a SecurityContext for the container
This change adds the Container object to both build and runtime Environments.
Compatibility is preserved -- the existing ImageURL field is still used. See the comments in types.go for the overriding rules in the case that both Container and ImageURL are specified.
Keep install docs in one place INSTALL.md instead of two.
Use github releases for all YAMLs and CLIs. This has a few advantages:
(a) it makes releasess more transparent
(b) all yaml/cli files are transferred over HTTPS
(c) CLIs and YAMLs being from the same release ensures that people
always get compatible versions (we will still occasionally break
api compatibility, until beta)
