caches: use single default cache dir for all backends. - disable .lower() on cache settings so uppercase directories are actually handled correctly. - fixed problem with long new dir structure that isn't yet existing.

exception-tracker: store event sending exception for easier event fail debugging.

core: added option to prefix cache keys for usage in cluster.

Added tag v4.13.0 for changeset 3d6bf2d81b15

release: Finish preparation for 4.13.0

i18n: Updated message catalog template

release: Merge default into stable for release preparation

translations: update messages catalog

docs: update API documentation

docs: updated packages.