Update all dqn... files to use functions

[Jmiceli17]

Most dqn-....py files in this repo are set up like scripts, they call main once at the beginning and then just step through the file. This is bad practice and looks messy. It'd be nice to put the actual training and logging in functions or something just to improve readability. It'd also make it easier to implement new methods because code would me more reusable.