script option for printing a limited number of fields (1..n) from rules

[karfau]

Use case: A a maintainer of a rule set I want to be able to reason about the currently active rules.
E.g. seeing all groups and documentation links for all active rules.

• Currently the available report contains more details which should also be availabe when reporting this way.
• it might be helpful to only print the filtered result to stdout when requested
• It might be helpful to have a --json flag for output
• filtering the entries by field will be dealt with in Allow the printed report to be filtered by certain fields #20