Master egamma eta restriction
This is an attempt to address ATLASRECTS-4233, in order to address pile-up dependencies of superclusters. @christos and @rnaranjo should comment on the direction this is going and suggest any code improvements. (One potential improvement is to make the L1 restriction more controllable by parameters--I might try to do that.)
This code has been tested to run, but there hasn't been any performance testing.