WatchMempol: fix a regression
PeerGroup: configure peer as download peer even when there is no chain, but don't configure download params as that would trigger block fetch.
Extract ECDSASignature.isCanonical() which checks for BIP62 low S value. Adds a test.
DefaultRiskAnalysis.isStandard checks for signatures to use canonical DER encoding and low S values. Adds a test.
Restrict access to ECKey.CURVE_PARAMS. The field is almost redundant. Parameters can be fetched from ECKey.CURVE as well.
Change the WatchMempool pool to build statistics about risk analysis. Removes the pay-to-pubkey detection which was in there.