Move SQLCipher support into separate repo

[mikemee]

Per discussion on #192, I'm opening this as a catch-all specific issue to track splitting out the SQLCipher support into a separate repo.

I need to extract SQLCipher support out into its own repo. It's causing too many problems when bundled.

This appears to affects several Carthage and Cocoa Pod build issues (e.g. #300, #308) as well as dependent features (#272), many of which could at least be isolated to just those who need SQLCipher.

[mikemee]

Completed via PR #314.

Replacement SQLCipher available for testing at https://github.com/stephencelis/SQLiteCipher.swift. Comments and PR's welcomed!