Server port allocation

[rbnpi]

Any chance of implementing the text file in .sonic-pi to allow easy allocation of port numbers, before 3.2 goes final, as indicated in the Server - breaking change - improve port detection and initialisation commit d245d93c5b797ad76fa333f829c32d67480af96c description. This is mainly to enable the server listen port to be fixed, so that programs like sonic-pi-cli which I have used a lot can be used conveniently. It is easy enough to do it directly by amending port-discovery.rb but this would not be easy for most users. The alternative is to use a port parameter with sonic-pi-cli, but you would have to look at the log to find the port first each time you wanted to use it which is cumbersome. The main thing is to be able to get a fixed port here rather than a dynamically allocated one.

[rbnpi]

I've now amended sonic-pi-cli to cope with dynamically allocated server port, so that particular problem is solved (see https://github.com/rbnpi/sonic-pi-cli)