current.ERROR single concept for global error messages

also:
- removing obscuring .permit hooks in S3Resource and S3RequestManager, using global reference current.auth.s3_has_permission directly instead
- action a ToDo in hrm, although this one doesn't seem to be used currently?

S3RequestManager does not seem to have a purpose other than to hold references to global constants and utility functions, which is confusing for new developers because other concepts e.g. current and s3utils.py are much more common, so i'd like to remove this class and replace its references with standard concepts

hope this is ok - ptressel (irc) seemed to agree