Track verified callbacks

[nickpatrick]

Android equivalent of https://github.com/radarlabs/radar-sdk-ios/pull/337

• Remove trackVerifiedToken() and change trackVerified() to return RadarVerifiedLocationToken
• Remove token param from startTrackingVerified() and change RadarVerifiedDelegate to return RadarVerifiedLocationToken
• Make token.expiresAt override interval if needed
• Add getVerifiedLocationToken() which will return last token if not expired and request fresh token if needed
• Random logging and comment cleanup to match iOS