Implement devfile parser

[kadel]

The goal is to have a package to handle devfile deserialization

• we need to create parser architecture that will handle parsing multiple devfile spec versions (currently there is 1.0.0 and 1.0.1-beta
• the design should ideally avoid logic duplication. It should be possible to share common code between devfile spec versions as the expectation is that the new devfile versions will be mostly just adding new files

from the implementation plan:

Create a golang library for parsing and reading data from Devfile
Devfile is versioned file so the design of a library needs to be able to handle and support multiple Devfile versions at the same time

Parser high level design:

• The parser would read the provided devfile.
• From the devfile, parser would look for the API Version of the devfile and validate whether the API version in supported in odo.
• The devfile schema is based on http://json-schema.org/draft-07/schema#
• Hence, the parser would validate the integrity of the provided devfile with the devfile json schema of the respective API version.
• Furthermore, parser would try to map devfile sections (projects, components, commands etc) to their respective Golang structs.
• The idea is to have same Golang structs for the devfile sections across different API version contingent to the condition that the sections themselves are compatible across the API versions..
• This is very similar to the way Golang structs are handled across different GVK versions in kubernetes. https://github.com/kubernetes/kubernetes/blob/ded2ff39c381b122951dd103dafb291755791921/staging/src/k8s.io/apimachinery/pkg/runtime/scheme.go#L32
• The implementation details for this with respect to odo are being worked upon and once confirmed would be updated here.

[kadel]

/area devfile