b2c.timeout: Add support for setting timeouts through the command line

This would be equivalent to having a bunch of REST calls made to the server at boot time, but more convenient for users who want to define their whole pipeline via the command line (the whole point of b2c, to be honest).

The reason this was not done as part of !86 (merged) is that I would like to prove the usefulness and usability of the feature and maybe add more timeouts before committing to the interface.