py3: switch to .items() using transformer .iteritems() don't exist in Python 3 world. Used the transformer to replace .iteritems() to .items()

py3: handle multiple arguments in .encode() and .decode() There is a case and more can be present where these functions have multiple arguments. Our transformer used to handle the first argument, so added a loop to handle more arguments if present.

py3: convert to unicode to pass into encode() encoding.encoding is bytes, we need to pass it to encode() which accepts unicodes in py3, so used pycomapt.sysstr() Also this can't be done using transformer as that only transforms the string values not variables.

templater: use "needle" and "haystack" as (meta-)variables for ifcontains() It wasn't immediately clear if it's supposed to look for "search" in "thing" or "thing" in "search".

copies: mark checkcopies as internal with the _ prefix

copies: split u1/u2 to u1u/u2u and u1r/u2r These will be made different in case of grafts by another patch in this series.

copies: style fixes and add comment

copies: limit is an optimization, and doesn't provide guarantees