Further refactoring of the Content Editor

With CHANNELMGR-2098 the buttons (save, discard, close) moved out of the content editor to the parent components (editContentMain, Step2Controller). The content editor can be further cleaned up for example by moving out the extra-message. The parent components can show those themselves instead of passing it to the content editor.

Possibly the functionality for cancelRequestPublication() can also be moved out of it.

And then: the watch that is used to toggle the loading indicator can also be simplified now that for example the save functions have moved to the parent component instead of being spread over content editor and other components.

Also: the confirmDiscardChanges function in the ContentEditor is now only used by the editContentMain controller. To fix CHANNELMGR-2098 the Step2Controller had to implement its own version of that. This method can now move out of the ContentEditor and move to the editMainController.