logging: use lazy parameter evaluation in log calls.

exception_store: rename .ini option for future

added some more logging for token auth

docs: deprecate beaker.cache in docs

core: use py3 compatible prints

svn: use streaming uploads/downloads of files. - before we buffered whole content before uploading/download - this could lead to OOM errors on big files - now instead we stream when PUT/GET are sent from SVN resulting in faster more efficient data transfer

svn: use shared configurable storage for svn_txn_id interception logic.

celery: use exc_tracker to store tasks exceptions for easier debugging.

exc_tracker: allow setting custom store via .ini file - use safer exc read when listing exceptions.

docs: updated scaling/cluster docs