3.0 - Updates for ApiGen and other general edits

Updated docblocks for ApiGen errors (https://github.com/cakephp/cakephp/issues/2677).  Replaced some `CakeNumber` references with `Number`.  Removed `serverOffset()` and `niceShort()` from `TimeHelper `since they've been removed from `Time`.  "Additional" typo correction.

Going to continue with this in another PR so that it's easily digestible - easing proofreading.