Remove dependency on deprecated t3lib

t3lib has been deprecated for a while and has been completely removed from TYPO3 6.2 LTS. However, the original classes are still present, albeit under different names. 

My patches replace all references to t3lib_* with the new class names. They also adapt the way flashMessages are handled in a controller to the current implementation in TYPO3/ExtBase.

All changes have been tested and confirmed to work on our production system.