Use level instead of CP

[Geljorgun]

A lot of the logic rules would apply better across the spectrum of pokemon if they used the pokemon's level as a condition instead of CP. For instance, I could set an easy rule across all pokemon to transfer anything under level 20 instead of having to enter in a different CP floor for every pokemon species. The "CP-based pokeball strategy" and minimum CP values for using berries in the Catching settings could also benefit from having an option for using the level as well.