Localization update

[Nomad00]

Observed when using DMPasscode on a device with Face ID configured, the key was being returned from the custom NSLocalizedString macro (instead of the localized string). This was causing a Non-empty localizedReason must be provided error to be thrown. The remedy for this is found in the 3rd commit below; the first 2 clean things up.

localization-update - Project settings modernization.

• Update iOS Deployment Target to iOS 8 (Minimum supported by Xcode 10).
• Apply recommended settings for the DMPasscode & Pods project.
• Enable Base Internationalization.
• Migrate “English.lproj” (Deprecated).
• Remove :exclusive => true from Podfile, as it is an unsupported option.
• Add platform :ios, ‘8.0’ to Podfile to resolve CocoaPods warning.
• Update podspec to version 2.1.0.
• Run pod install from Example directory.

localization-update - Implicit self warning resolutions.

• Add self -> in a number of places to resolve warnings.

localization-update - Resolve NSLocalizedString macro collision.

• Remove NSLocalizedString macro, as it was causing issues when leveraged from Swift code.
• Refactor calls to above macro to instead use NSLocalizedStringFromTableInBundle directly.
• Add NSFaceIDUsageDescription to example app Info.plist.
• Closes #39
• Closes #38