Allows server modders to hook into basic player events

The message gets printed very often on some maps/servers (e.g. Multeasymap), which may lead to lag (#200), though I didn't notice it on my machine. It also gets printed even more often when playing demos and skipping to a specific point, causing the game to hang for multiple seconds. For debug purposes, this message was not very useful anyway, as "debug 1" will enable a more useful error message: https://github.com/teeworlds/teeworlds/blob/05235cd6467df4f74dcc52e1aa698c83767930db/src...

The server list was being filtered and resorted for every new entry being added. Now the resort is deferred until the next update call, so multiple entries being added in the same frame will not cause significant lags. There is only a minor FPS drop now when refreshing the server browser with br_max_requests 250, 20 server filters and using the quick search at the same time. Closes #3051.