Update default ports

[shuse2]

Description

Ports used in P2P / RPC and in plugins should be distinguishable. ie) in different range.
Below should be default value on each port

P2P: 7667
RPC: 7887
Plugins: 8000-

After this change is implemented, lisk-core configs and seed nodes should be updated to follow this default values.

Motivation

In lisk-core, we have different ports for different network, but we no longer require them and it is hard to remember which network has which port open.
Also, this introduces requirement to have different default configs for each network.

Acceptance Criteria

• All default values are updated as specified above