Multi-instance management

[Alloc]

Separate instance-specific configuration (e.g. port) from generic one (e.g. Steam logon) and add appropriate functionality to the management scripts so that a single set of script files / engine can run multiple instances of 7dtd on the same machine with different settings.

[alloc]

In 9:

Fix #1, #2, #3, #5; Refs #4, #6: WD works for save path, not for some logs

[Alloc]

As of A8.1: Logs are always stored within the engine directory:

7dtd/logs/connection_log_25000.txt
7dtd/logs/content_log.txt
7dtd/7DaysToDie_Data/output_log.txt

Apart of that it might already work.

[Alloc]

output_log is stored in instance path with native Linux engine, connection + content log are by Steam and their location can probably not be controlled. Should not matter though.