Change the default port numbers to avoid the ephemeral/dynamic range

[achimnol]

The current defaults are:

• monitor (termui): 50101
• monitor (webui): 50201
• console: 50102

Since these are inside the default ephemeral/dynamic port range used in Linux and many other operating systems, there are rare cases that aiomonitor causes failure of the application when the host is busy enough to handle many concurrent client connections.
(I actually experienced this situation in one of my customer sites....)

ref: https://en.wikipedia.org/wiki/Ephemeral_port

I'd like to change them to:

• monitor (termui): 20101
• monitor (webui): 20102
• console: 20103

As this is a potentially breaking change for some users who have been relying on the defaults, I'm leaving this as an explicit issue.