ValueCache::addValues no longer emits an expire callback for the
old version when a value is edited; only the add callback for the
new version is emitted.
Add a grace period in expireValues when the cache is synced, using
the value type's expiration as an extra margin before emitting
expirations.
OpValueCache::onValuesAdded: on edit, expire the old value and add
the new one without incrementing refCount.
SearchCache::get: only serve from cache when synced.
Adrien Béraud
88af795eaa