Community Templates UI: Accept yml and github directory locations

Background

When entering in a template, we would like to be able to enter either (1) the full url path to a yaml file (2) the package name of the github directory (e.g. for https://github.com/influxdata/community-templates/blob/master/kafka/kafka-template.yml we want to give them kafka).

Acceptance Criteria

• the UI's url upload input accepts file paths and directories
  • it accepts arbitrary yaml / json / jsonnet files from the web
  • it accepts directories from our community templates github repo (e.g. kafka resolves to https://github.com/influxdata/community-templates/tree/master/kafka)
    • it looks for readme.md and manifest.(yml|yaml|json|jsonnet) files

WHEN I use template directory that does not exist in the community-templates repo
AND the templates schema directory doesn't match the required directory structure
THEN I should be informed that this template requires entering the URL directly