Add DefaultCheckMemPool chain parameter
Get rid of RegTest()
Move majority constants to chainparams
Add AllowMinDifficultyBlocks chain parameter
Add RequireStandard chain parameter
Add RPCisTestNet chain parameter
Get rid of TestNet()
Replace virtual methods with static attributes, chainparams.h depends on
protocol.h instead of the other way around
net.h was using std namespace through chainparams.h included in protocol.h