My Swift extensions

Here are my Swift extensions, as well as changes needed to make Lumberjack more Swift-friendly.
After some thought, I realized I might have been a bit overzealous in replacing `LOG_FLAG_...` In that if someone else had, say `LOG_FLAG_ERROR` defined to something else, the developer would need to re-define `LOG_ERROR` and `LOG_FLAG_ERROR`.

Then again, the use of framework modules may change this. If so, we can probably change the `.moduleMap` file accordingly.