Add options for automatic quiet time widget and preferred replacement index

[ScottyDoesKnow]

Adds options to show quiet time widget when quiet time is enabled, and to pick which widget is replaced when there are no empty slots.

## Notes to Reviewer

I spent far too long modifying this quiet time icon, but I believe it will need an attribution to use.

I added a preferred replacement index and modified how the code looks for the best index to use. Basically this is just because I'd rather it replaced index 2 instead of 1 for my personal use, but I also figured it only made sense to replace the first bluetooth-related widget for the bluetooth disconnection widget and not for the battery or quiet time widgets. I can always remove this if you disagree.

There are a couple TODOs in the code. The first is because I don't know much about the different versions and whether there should be checks to see if the quiet time feature is available or not. The others are related to pebble round, because I don't know if it only has two slots and shouldn't allow a preferred replacement index of 1, and because I can't check PBL_ROUND to change the default preferred replacement index in index.js.

I also did some minor cleanup in code near my changes, let me know if that bothers you.

[tilden]

Thanks for the MR!

So the code looks good, but I'm actually still not completely sure if this is the approach that I want to take -- I've always felt like the "status" system should be improved. For example, I had the thought there could be a dedicated "status area", where the user could optionally always show bluetooth status, quiet time status, low battery warning, etc:

(not really final, but just to illustrate sort of thing I was thinking about)