Improve documentation

[ffried]

There are a few things that should be improved in the documentation:

• Upgrade to new standards (iOS 12)
• Add documentation for changes Use static const for default log level so Swift can strip strings #952 (this one is on me)
• Improve documentation for Swift
• Maybe adjust documentation for Merged framework targets + using xcconfig + deployment target iOS 8 and Mac OS 10.10 #959 (/cc @bpoplauschi)

[bpoplauschi]

@ffried good list.
I would add

• look into deprecating DDASLLogCapture along with DDTTYLogger and DDASLLogger for the newer OS versions.

[ffried]

Good point. Although that requires some code changes first. But yea, we should also mention that in the docs then.

[bpoplauschi]

Linking #759 and #757 to the documentation updates needed

[lolgear]

• use __auto_type inference in documentation. (?)

Yes, auto type inference has its own downsides ( time spent by type deducing ).
But wait, it is what whole Swift does every second.
And yes, for examples it could be acceptable.