[TASK] Use ModuleTemplate in ext:lang

Ext:lang uses ModuleTemplate API and BackendTemplateView for
its Backend Module.

Change-Id: I1497d9bdd326114cff70fd723d0bbbdefc16fdf9
Resolves: #69844
Relates: #69841
Relates: #69842
Releases: master
Reviewed-on: http://review.typo3.org/43351


Reviewed-by: Daniel Goerz <ervaude@gmail.com>
Tested-by: Daniel Goerz <ervaude@gmail.com>
Reviewed-by: Frank Nägler <frank.naegler@typo3.org>
Tested-by: Frank Nägler <frank.naegler@typo3.org>
Reviewed-by: Morton Jonuschat <m.jonuschat@mojocode.de>
Tested-by: Morton Jonuschat <m.jonuschat@mojocode.de>
Reviewed-by: Stefan Neufeind <typo3.neufeind@speedpartner.de>
Tested-by: Stefan Neufeind <typo3.neufeind@speedpartner.de>