Use defaultdict to simplify server and channel maps

[threedliams]

defaultdict is a python datatype I wasn't familiar with when originally building this, it allows you to specify a default value that the dictionary gets initialized at to avoid having to check if a key is initialized before adding to it. This would simplify the creation of the server/channel maps a bit

[threedliams]

See https://docs.python.org/3/library/collections.html#collections.defaultdict
And
https://www.accelebrate.com/blog/using-defaultdict-python/
For more info.

Basically we want to use defaultdict to eliminate the need for all the "if key doesn't exist then initialize key" statements since it can automatically initialize any new key to "". So instead of that if statement we can just use += without having to worry about initialization