config: add flag values automatically (#17)

Add mechanism to automatically add flag values based on the config struct.
The default value is inferred from the provided struct.

Currently, no help text is added to the flags.

docker: add Dockerfile (#14)

Add docker file and describe how to use dockerized boa.

fmt: improve formatting (#12)

Improve formatting of templated code.
Add a newline when printing an error in the root command.

test: add golden files (#10)

Add golden file tests for the 'add' and the 'init' command.