- Refactor directive

- Basic implementation

Update/angular

Also restructure files containing interfaces.

Octal characters are deprecated and don't work anymore. This solution 
uses an empty string over the whole line.

#502

- Add ReferenceManager to check if deleted elements are referenced 
anywhere in the unit. If so display a warning.
- Move page logic to UnitService

Update/translate package

- A suitable version was not available after update of Angular
- Reactivate test for valid pages

#499

- Background color must not be transparent for the stickied panel to 
overlay properly.

- Use TextImagePanel where possible

Toolbar is a single word, therefore any capitalized letters are errors. 
No need to sanitize, since this was broken anyway.

#384

#386

... instead if setting the value directly on the object. This way 
elements can react to ID changes. This is necessary for DropLists since 
a changed ID has to be reflected to child elements.

#445