- added new OCA.Files namespace for files classes
- the sidebar can now switch between views/containers
- the trashbin renders in its own container but currently doesn't work
  due to overrides
- added app.js as entry point for JS code (ideally all other files should
  only contain classes and not trigger anything)

reduce code duplication, fix parse error, prevent page reload on hitting enter while changing the display name - refs #8085

adding xit to globals

- Also fixes a few JSHint warnings in files app
- Added "global" comment on top of files app to suppress warning and
  also inform devs about what globals are use