Single/Double currency bootstrap preset

[fboucquez]

At the moment, the default bootstrap preset defines 2 currencies, the main (cat.currency) and the harvest one (cat.harvest).

I would like to change the bootstrap preset to a single currency like a public/testnet by default. In addition, I would add more bootstrap/private's assemblies. The options could be:

• -p private (all nodes - single currency)
• -p private -a dual-currency (all nodes - dual currency)
• -p private -a light (min services - single currency)
• -p private -a light-dual-currency (min services - dual currency)
• -p private -a demo (faucet, explorer, etc services - single currency)
• -p private -a demo-dual-currency (faucet, explorer, etc services - dual currency)

(It easier and cleaner to add a harvest currency via assembly than to remove one)

I would also change the default network type of bootstrap from public test to the new private test (this is just a flag change, all the default addresses are generated)