Overhaul of DMX setup and utils

[mtlam]

Discussed at our second pint_pal refactoring meeting, we want an overall overhaul of dmx_utils.py and how things are run in dmx_setup(). We should convert this to a class structure, make sure to rearrange the logic, and also avoid duplication where possible. Much of this is hashed out/already looked into in #107.

[rossjjennings]

I will point out that in #107 I was mostly concerned with "low-hanging fruit" ideas to make things faster. So far, I haven't made any effort to overhaul the logic or code structure of dmx_utils.py, I've just tried to speed up the slowest parts.