Consider adding data as a parameter for indicator calculations

[dave-mills]

The current set of indicator calculations requires a data dataframe to exist. This is fine, as we can make sure it does before calling the functions. But I think it would be more flexible to pass in a data object as a parameter (similar to our graphics functions).

This way, we can pass whatever filtered dataset we need to calculate the indicators for one team, for many teams, for one group, etc.

This is also linked to #9