Code coverage reports and goals

[MikeSmithEU]

(related to #14 )

What reporting strategy do we want to use for this, looking for more input and volunteers to take this on.

• What percentage of code coverage would we find acceptable (assuming 100% is the gold standard that we will strive for, yet may not achieve)?
• Do we only merge Pull Requests if we have e.g. 90%+ code coverage?
• Should this be our first next goal for the existing codebase before we continue with extra development?