Implement user timezone listener

[leevigraham]

Date Time + Timezone Reference Links:

• User-Specific Timezones With Symfony2 and Twig Extensions
• Storing Date/Times in Databases
• Working with DateTime Instances
• Symfony2: Where to set a user defined time zone
• How To Synchronize Your PHP and MySQL Timezones
• http://symfony.com/doc/current/reference/forms/types/datetime.html#model-timezone

Also need to determine if the event should be security.interactive_login or kernel.request. Pretty sure it should be kernel.request

• Login event listener in Symfony2
• Making the Locale "Sticky" during a User's Session