v2.1.0.11

This release introduces the new SIGMA PoW algorithm, a 'CPU friendly' algorithm designed to better suit Guldens needs than the previous algorithm scrypt that was used before.

CORE - Introduce new utility 'bench_sigma' for testing/benchmarking SIGMA outside of the Gulden app itself.
CORE - Fix DOS vulnerability (crash) in witness bundle input checking
CORE - Introduce SIGMA as the new PoW algorithm in testnet builds.
CORE - Minor improve to Delta difficulty adjustment algorithm to work better with SIGMA
CORE - Introduce new/modified reward schedule for development funding and slight increase in witness rewards (as per GAB decision)
RPC - Modify 'setgenerate' command to take a memory paramater for SIGMA
RPC - Improve output of 'getnetworkhashps' command