[BUGFIX] use Date.format helper instead of DateTime::format

Without this change, Eel throws an error because DateTime::format
cannot be called because the protected context is used.
[BUGFIX] if no dimensions are configured live indexing is broken

without this change, updating the index when a node is modified will
not happen if no dimensions are configured.
Merge pull request #5 from skurfuerst/master

[TASK] Adjust to changes in Neos master