[TASK] Adjust translate view helpers to Neos master

The translate view helper will now assume that the current package is
TYPO3.Neos - therefore the package key must always be declared in plugin
templates.
[BUGFIX] Fix Gravatar default icon

Due to a change in the resource handling in Neos, a wrong URI was
generated for the Gravatar default icon.

Also replaced the old icon (TYPO3 logo) by a better one (person).
[BUGFIX] Hotfix for rendering an RSS feed without wrapped divs
[FEATURE] Allow to include full post content in feed

By setting the feed.includeContent flag to TRUE, the full content of
posts will be included in the feed.