[TASK] Removed event repository in EventIndexController

The repository was not used and therefore removed.
[TASK] Fixed return type of date getters

The getStartDate() and getEndDate() methods in the EventIndexController
return Tx_CzSimpleCal_Utility_DateTime objects, so the invalid
DateTime return type in the PHPDoc was replaced.
[TASK] Removed some obsolete injectors

Since Extbase supports the @inject annotation the obsolete injector
methods were removed and replaced with @inject.
[TASK] Fixed method return types