Move network-time related functions to timedata.cpp/h

The network time-offset-mangement functions from util.cpp are moved to
timedata.(cpp|h). This breaks the dependency of util on netbase.
Remove unnecessary dependencies for bitcoin-cli

This commit removes all the unnecessary dependencies (key, core,
netbase, sync, ...) from bitcoin-cli.

To do this it 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.