CB-6570 FFOS privileged apps compatibility

All tests are now compatible with FFOS privileged apps (CSP restrictions)

- inline scripts moved to JavaScript files
- added addListenerToClass function which is used to connect buttons with test functions.
- moved test initialization to JS file (for DRY and privileged apps compatibility)

Please check it on all platforms and r+ if working. There should be no change in behaviour of the app.