Reddit post generator

Adds a way to use a post template to generate a post for reddit and post it directly.

Templates are of the format:

```
IP: {{generator.address}}
Starts: {{startsUTC()}}
Opens: {{opensUTC()}}
```

- [x] Saving settings across loads
- [x] Parsing of chosen template
- [x] Posting to reddit with correct title + parsed template
- [x] Template editor/preview