Get rid of all hardcoded mpsc::channel capacities

[niklasad1]

Related:

• [ws server]: hardcodes number of concurrent tasks to 8 #168
• merge v2 to master #180 (comment)

http-server/src/server.rs:165:          let (tx, rx) = mpsc::channel(32);
http-server/src/server.rs:190:          let (tx, rx) = mpsc::channel(32);
http-server/src/transport/background.rs:67:             let (tx, rx) = mpsc::channel(4);
ws-server/src/server.rs:194:            let (tx, rx) = mpsc::channel(32);
ws-server/src/server.rs:219:            let (tx, rx) = mpsc::channel(32);
ws-server/src/transport.rs:310:         let (to_front, from_connections) = mpsc::channel(256);
ws-server/src/transport.rs:352: let (to_connec, mut from_front) = mpsc::channel(16);

[niklasad1]

Fixed by #253 #174