Remove code that was needed for old Chrome support.

Chrome versions prior 24 did not support opening database with version and
use of upgradeneeded event. Instead it implemented older version of the
specification. Now the code supporting older versions is not needed so
clean-up the code.
Change .on* to use of addEventListener.

Where using request.onsuccess, transaction.onerror or other similar
parts, change to use adeEventListener and appropriate event. Just to
make code look cleaner.

Also do other minor code clean-up changes.
Re-enable AppCache manifest.

Enable AppCache manifest and update timestamp in notes.appcache file.