[BUG #6968] need to add JSDoc comment in front of additional class in file

- actually, an empty JSDoc would suffice, as this somehow links this statement
  to the top-level qx.Class.define, which has sufficent @ignore's
- (this is somewhat surprising, but i don't worry too much about the implications
  here, it's only test code)
[BUG #6968] add special section for @ignore to manual

- mostly from corresp. blog post
[BUG #6968] remove @ignore(simulator) from skeletons

- as it can negatively affect dependency resolution for the 'simulation-build' job
- rather, add "simulator" to allowed-globals in config
[BUG #6968] adapted @ignore's to new 'lint' config in Feedreader
[BUG #6968] adapted @ignore's for 'lint' job in Simulator
[BUG #6968] adapted lint.py to use Hint() tree

- also some clean-up for global_symbols.py
[BUG #6968] fixed lint issues for Playground, Showcase, Widgetbrowser
[BUG #6968] fixed lint issues for Demobrowser

- delegate 'lint' job to config.demobrowser.json, to take advantage of "libraries"