[WIP] Opera 12 support

This is mostly ready for testing.

TODO:

- [x] Fix console button
- [x] Fix YouTube expandos
- [x] ~~Investigate statically concatenating files instead of `loader.json`~~
   - Grunt has `grunt-contrib-concat`
   - Concatenation approach results in weird JS errors.
- [x] Fix imgur expandos
- [x] Fix YouTube expandos in comment pages
- [x] Fix Imgur album expandos
- [ ] Testing
- [x] Automated tests