Remove all unnecessary dependencies for bitcoin-cli

This commit removes all the unnecessary dependencies (key, core, netbase, ...) of bitcoin-cli.

To do this:
- Shards the chain parameters into BaseParams, which contains just the RPC port and data directory (as used by utils and bitcoin-cli) and Params, with the rest.
- The network time-offset-mangement functions from util.cpp are moved to nettime.(cpp|h). This breaks the dependency of util on netbase.