v11.19.0

• DexSnapshot.WithoutOffer(string offerIndex) returns the snapshot without one offer, its DexIndex derived from the snapshot's (SnapshotRoll.WithoutOffer, the DexIndexDelta the roll uses) instead of built at the next evaluation (#310). The index is matched in either case; a snapshot that does not hold the offer is returned as it is. Only Offers changes: owner counts, sequences and balances are left alone. DexSnapshot.WithoutOffer(string offerIndex, bool releaseOwnerReserve) also lowers the owner's OwnerCount by one, never below zero and only for an owner the snapshot lists, with the account patched into the derived index; SnapshotRoll.PatchAccounts takes the DexIndex instead of the DexWorld
• Docs: Amounts-Guide (both languages) describes WithoutOffer and releaseOwnerReserve for an OfferCancel and for taking out a placed remainder
• Tests: TestUSnapshotRoll takes out a placed remainder that was the only offer of its book, an offer mid-book, an offer named in lower case and a hybrid offer from both its books, comparing each derived index with one built afresh and the next result through it with one through a fresh index; an offer the snapshot does not hold returns the same instance. With releaseOwnerReserve it takes out a placed remainder and checks the owner's count is back to the one before the OfferCreate, the derived index and the next result, a count already at zero staying at zero, and an owner the snapshot does not list not being added