Move mode setting into a project global

[ntelfer]

We need to move away from passing the servers current mode into relevant functions and instead set the mode globally. It is to difficult to enforce that the mode gets passed to all areas of the code base. This is a global setting that the Didery code should only ever read, as such it should be in a globally accessible location.

[ntelfer]

Also remove all hard coded strings for the current three modes. ("method", "promiscuous", "race")