Fix js binding problem with MultiFileUpload for Directories

Because ProxyPanel does not forward addBinding-function calls to proxy-item
GMaps has to invoke callOnContentReady because it reloads marker-infos

Before it didn't load images placed in marker-info
Ext4 Menu: add class to allow custom styling
Models: add new expression: GroupConcat and Child_GroupConcat

behaves like mysql GROUP_CONCAT()
Rest controller: use expr for better performance
console might not be set in all browsers (IE)
Fix Cards Generator: parentData can be an Component_Data object
Ext4: cleanup; remove unused event
Ext4 Controllers: verify required arguments and raise appropriate errors
only update old columns to new when data was found
add translation
use ext4 each, required if no ext2 is loaded
search for anchors in linktag intern recursive for all childcomponents
Use cls-attribute in html-select-field

It was possible to set but wasn't written to html.
Extensible: add translation
Simplify translation in Columns Component