Test for build context

This variable was a temporary measure from https://github.com/scitran/core/pull/190 and never fully removed until now.

- Install pip requirements in Dockerfile
- Pin the versions of the documentation pip packages.
- Rebuild docs on launch of uswgi

closes flywheel-io/flywheel#169

add new ENV required variable

- Update bootstrap.json to bootstrap-dev.json to reflect new convention.
- Move bootstrap-data.sh to PRE_RUNAS_CMD var to reflect it's need to be run as root due to pip install.

- Entrypoint has new $PRE_RUNAS_CMD that allows running of root tasks before dropping privs.
- Added $SCITRAN_RUNTIME_PROTOCOL for explicit designation of http vs https.
- Updated README.md examples.
- No longer using requirements_dev.txt due to long install time.

Not happy with baking the pip requirement into the container. Need to think more.
Also, instructions in docker/README.md are broken.

Don't reference branches from within source. This allows core and testdata repo to move without breaking not up-to-date versions of core. Also allows branches to be fully merged.

Still a similar branch reference in bin/run.sh

Now supports API enabled bootstrapping.

This will create a generic image that has a single external dependency of a mongodb instance. Example usage is included in the README.md.