Separate out config information

[triangle-man]

Put site-specific information in a config file somewhere. Presently, this is:

• The URL for Forecast (currently in forecastRaw.ml)
• The organisation name and repository name for GitHub (currently in issues-by-project-graphql.graphql, so maybe that's okay for now)
• The GitHub "project" name (currently in schedule.ml)

[triangle-man]

As a first step, we could hard-code this all in config.ml.

[mhauru]

Done in https://github.com/alan-turing-institute/whatwhat/pull/56