This is an experimental port of kyuupichan's 'Reboot nolnet' patch [1].
Features:

• -chain_nol parameter to start on nolnet (port 9333)
• New network bytes so we don't interfere with previous nolnet nodes
• P2PKH addresses begin with B and P2SH with U
• BIP32 xprv and xpub prefixes are "Big " and "Blks".
• After 20 minutes difficulty resets to 1 like on testnet3

BU's CreateGenesisBlock() has been renamed to BU CreateGenesisBlock()
to avoid collision with Core's CreateGenesisBlock() which has been left in
until a further refactoring patch.

There are a number of FIXME's in the code which will require resolution.

[1] https://github.com/BitcoinUnlimited/BitcoinUnlimited/pull/642

Read the NOTE before you run on nolnet.
When you do, you need to set you EB to 16MB since there is already
nearly 9MB block (last checked today by someone else) in the nolnet chain.

bitcoind -chain_nol -excessiveblock=16000000

Some points:

• Check that you can do a successful sync from scratch.
• Check that you can stop/restart and carry on.
• Check that you can send/receive (ask others to provide you with some testcoins as you might not be able to mine yourself).
• Check if you can spot any problems relating to nolnet operation of your client, and raise Issues if you do.
• Feel the joy of mining your own coins again (if you have mining hardware or can figure out how to CPU mine via the RPC).
• Check what happens when you run with too-low '-excessiveblocksize' (you should start banning peers with bad-blk-length reasons).
• Check whether increasing the limit gets your node in trouble.

CAVEAT: ABC (based on Core 0.14) pruning implementation is not yet
adapted to handle big blocks. Calculate extra space as it will
scale the prune=XXX value by as much as the average block size
exceeds 1MB.