Refactor settings dialog code
This moves the code for each tab into its own file. The main.c file has been a complete mess for quite a long time. The background tab file is still larger than I'd like, but that will have to do for now.
This moves the code for each tab into its own file. The main.c file has been a complete mess for quite a long time. The background tab file is still larger than I'd like, but that will have to do for now.