Properties customHtmlId, customCssClass: Improved validation regexp
NodeTypes: groups re-organised to make them more intuitive for end users

The initial idea was to reflect the structure of Foundation and how they categorise modules. This seems to be ineffective for CMS end-user.
Button: split into 2 node types: Link and Button
Neos ContentReferences: inline editable (experimental!) + extra DIV wrapper removed
Button/Link: title attribute added with ability to set it via inspector
Title attribute added to some node types (container, grid, column) to easily reference them (e.g. via ContentReferences)