Import and update the talent repo from GitLab

[dfsnow]

The talent repo from GitLab represents the overarching plan for human development within the Data Department. However, it is badly out-of-date and needs some love. Specifically, we should:

• Import all the content there into this repository
• Update the set of core competencies (drop Shiny, add command line, etc.). Should reflect the competencies outlined in the wiki handbook
• Update the ladder/track, as certain positions have been added/removed
• Clean up all supporting documentation and files