support .devfile.yaml and parse from a path

[yangcao77]

Signed-off-by: Stephanie yangcao@redhat.com

What does this PR do?

Supports parse from a path which contains devfile.yaml or .devfile.yaml
If the path/url does not ends with .yaml, than assumes the value is a directory, and will check for devfile.yaml or .devfile.yaml under that directory
devfile.yaml takes priority than .devfile.yaml

What issues does this PR fix or reference?

Fixes devfile/api#61

Is your PR tested? Consider putting some instruction how to test your changes

manually tested

[maysunfaisal]

Should we think about adding Populate() unit tests for these use cases? WDYT

[openshift-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: maysunfaisal, yangcao77

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