Change server behavior when port by local is set to 0

[BxOxSxS]

Server will search for unused port within range of min_port and assign it to local
If there is no available port it will throw an error

Resolves #23 and gives easy way to implement max port which is my next plan

I tested it on linux and windows and everything seems to work great.
If the quality of the code needs to be tweaked feel free to tell me. I am quite new to rust. Unfortunately I'm going away for the weekend so most likely I will be able to do possible corrections on Monday or Tuesday

[ekzhang]

Unfortunately I don't think it's desired to look through every port in the range and manually try to bind a TCP listener up to 65536 times. The current behavior is as intended, a safeguard to prevent users from requesting specific ports that are small (~1024).

[BxOxSxS]

I really find these changes useful in case of managing bore. The Only thing that came to my mind how it could be improved is storing ports is some kind of slice and doing faster checks by checking if it's inside. It would require more memory but search would be a bit faster. But in my current code it's still quite fast (1000 ports in about 20 ms)