XWIKI-12741: The application code and data spaces should be nested inside the application space

* Bulletproof the AWM wizard
* Extend ApplicationCreatePage page object to be able to create a page in a nested space
* Extend ApplicationsLiveTableElement to be able to check if an application created in a nested space is listed
* Bulletproof the #livetable Velocity macro by properly escaping the live table id depending on the context (HTML, JavaScript)
* Fix Prototype.js to be able to call $(id) with an id that contains backslash