Initial devfile common library support

[elsony]

Provide an initial set of common library that can be used by various tools, e.g. odo, Che, dev console, for interactive with devfile and devfile registry.

This item contains:

1. Devfile parser to allow read and write of devfile (Create common library for devfile read and write #144)
2. Validator to provide validation that cannot be covered by schema validation
   • must be applicable to all tools, i.e. non-tools specific
   • e.g. starterProject cannot have multiple remotes defined
3. The specific functions required by the dev console (that is outside of devfile 2.0 spec but target for devfile 2.1 spec)
4. Devfile registry access
5. Index.json parser for accessing devfile info in a registry

[elsony]

Removing dup items that was created when github gives error on issue creation.