[FIX] propagate context through stock.move.action_cancel()
[FIX] Add missing context to some calls
[FIX] pad: improve pad bootstrap, prevent creating useless empty pads, avoid edition warning in read-only mode for new pads, translate messages

Added a small method to detect the proper server configuration,
and make it degrade gracefully if the method is not present.
This avoids having to force a pad URL generation in order to
test the config (possibly creating useless pads).
Add a user-friendly message when the pad has not yet been
initialized for a given record, in read-only mode.
[MERGE] [FIX] stock: add some missing context, courtesy of Lionel Sausin (Numérigraphe)