Speech synthesis, Night mode, Remember reading position, ...

* speech rate can be modified on per-language basis, but only in source codes; there's no interface for that

Targets these issues:
* #23 
* #12 
* #25 
@gyim:
> Please refactor this, it is kind of a hack to enable of0bf in settings and change it back :) An idea: BRPrayer could have an `optionOverrides` property that overrides the user settings.

Well, that's a bit difficult with the current architecture - I don't like `updateWebViewContent` method, which depends on global state instead of showing content from method's parameters. If we move towards more "functional approach", it would be easier. By "functional approach" I mean using only method's input parameters and not relying on any global variables.

The problem is that `BRSettings` is a singleton, so I can't make another instance and pass it to the method as its input parameter. If I want to pass all settings as a parameter, I would have to extract them to dictionary and not use the object... which is something I'd rather avoid.

If you find some time for this later, please feel free to refactor this. Maybe later I'll find some time to do this properly - I fully understand it's a dirty hack (and I wanted to add a comment of apology there, but I forgot :) ).