CMSPageBundle: Added bootstrap-wysiwgy html editor.

Another try at an editor, eh?
CMSPageBundle: PageCoreJS: Block.generateElementId() added.

When a block is created in the browser, the BlockView will now use CMSPageCore.blocks.generateElementId() to generate a valid id. This will also need calling after a sync to the back-end server (when the block gets a REAL id).