Improved Locale Switcher Performance

With a larger amount of sites, the Locale Switcher caused serious performance issues. Because the derived content calculation is performed on tab opening, the editor was forced to wait until this calculation has been finished. The dropdown now loads the variants when it is expanded. Additionally, the calculation has been improved so that a lot less request are required now. However, be aware that when opening the switcher the first time, the calculation may take a little bit longer, because the client needs to load and cache the folder structure of the variants once.

(CMS-22227)

Added Extension Point for Image Editors Forms

The image editor hotzone form is shown in a separate component called ImageMapEditorTargetEditors now. The form can be extended by writing a NestedRulePlugin for the ImageEditor component.

(CMS-14741)