[!!!][TASK] Improve default configuration handling

The configuration is centralized in the TypoScript configuration. The
TypoScript configuration is split into different directories for each
Extension.

The TSConfig is for the tt_news extension is only included if the
Extension is loaded.
[BUGFIX] TYPO3_MODE constant in ConfigurationManager

The detection of the TYPO3_MODE in the Backend is fixed. Before the
string "TYPO3_MODE" was used for comparison.