Added proper API Doc tags to all the `cache` modules so their respective pages on the site are built. Fixes #2530995

Added proper API Doc tags to all the `cache` modules so their respective pages on the site are built. Fixes #2530995

[fix #2529572] Support disabled localStorage FF3.6. FF3.6 bug causes JS error when accessing win.localStorage when it has been disabled in the browser. This commit wraps such calls in try/catch to prevent such an error.

APIDOC: Documentation of entry object properties.

[fix #2529141] Move expires CacheOffline -> Cache.

Fix CacheOffline Date handling. Date values now converted to msecs for localStorage serialization.

initOnly -> writeOnce:"initOnly"

Code review feedback. Remove unnecessary validators. readonly -> readOnly. Each OfflineCache instance sandboxes its entries from other instances. Fire "error" event for quota exceeded. Add static flushAll() method.

Store cached and expires values as Date. Expires Attribute can be set as Number or Date. Cached and expires values are stored as Dates in entry object, are serialized into String for localStorage, and then converted back to Date on the way out.

I <3 unit tests. DataSourceCacheExtension initializer was being called twice. Entry property "cache" is now a Date instead of a Boolean.

New: cache-offline code and tests.