Callback enhancements and Logging

[elixias]

• Rewrite properDB.js to provide 2 functions 1) execute a command for a result (for SELECT) 2) execute a command and run success/error callback (for add, delete, etc)
• Let user set myDB.log = true/false, true will print out SQL statements onto the log console.

[elixias]

http://html5doctor.com/introducing-web-sql-databases/

• Rewrite properDB.js to chain queries and execute only when .commit() is called or equivalent. And rollback by returning true/false in the error callback.