Join cache refresh

Added join cache automatic update when the joined table is
filtered/altered: A filter applied on the join destination (usually a
DB table or a csv) will impose a refresh of the join cache in the
source layer(s) -> all join caches are always kept up to date and
syncro with the joined database filter.
A global refresh action (e.g. triggered from the view menu) also
triggers a refresh of all Join caches