Add: getItemOffset to pagerInterface
ADD: getItemOffset to defaultPager
CHG: PagerCollecrtion now uses getItemOffset Method of default pager
CHG: DataBackends use the pager method getItemOffset to retrieve the offset
FIX: add new methods to test mocks
DEL: unneccessary test
CHG: raise TYPO3 version dependency to 6.1.99
CHG: typo3 version
FIX: tests, warnings, ...
Merge branch 'develop' of gitlab.pluspunkthosting.de:pt/pt_extlist into develop

* 'develop' of gitlab.pluspunkthosting.de:pt/pt_extlist:
  CHG: raise TYPO3 version dependency to 6.1.99