Changes with Aloha.Editor 0.24.38

Bugfix RT58552

Buttons in the toolbar, that have a dropdown menu would display the arrow (for opening the dropdown) slightly misplaced in firefox.
A css setting of the ui-plugin has been changed to fix this.

Bugfix RT58532

Contenthandler plugin: Fixed handling of empty block elements
When adding an empty paragraph with IE Version 8 or greater, the empty paragraph was not visible in the content after editing.
This is because empty paragraphs are not rendered in the browser. For editing, a
is added to empty paragraphs to make them editable.
Now, a
is added in the resulting content, so that it matches the expected WYSIWYG behaviour.