refactored inv and added inv_activatable
Add a missing case for invlet reshuffling on force invlet assignment.

Fixes issue #2672

There's a tiny other change in there, which is to remove a duplicate call of update_cache_with_item(). The call is unnecessary if reuse_cached_letter is false, and if it's true, the call will be made anyway.
Mark a couple missed strings.
Confirm that data/raw/sokoban.txt does not need translation.
Fix missing final profession in profession list.
iuse::knife: menu() didn't end in NULL but only crashed when built with -O. Also, remembers last menu selection (runtime).
restore: items and monsters save to json

This is stable/tested and was merged in 21e76f9, however removed later. Please test
Ensures that pickled stuff in fridges is properly sealed.
fixed minor memoryleak
Merge some bugfixes.
Merge inventory handling cleanup, i18n tweaks, pickles in jars, and memory leak fix.