Bootstrapdata from actual Teamcity server

- At startup, the server will fetch builds, buildTypes and Projects
from an actual TC server (the official jet brains one) and add docs to
the tasks collection.
- Set USE_BOOTSTRAP_DATA environment variable to use the old, hardcoded
bootstrap data.
This function might be doing a tad too much and it has side effect that are not clear when just viewing the declaration. It's both getting stuff from somewhere and then updating/inserting into a collection. Perhaps breaking out the HTTP-stuff into its own function returning some value and having that be the async part with futures?