Fixed issue with contentBox being left in Y.Node._instances after deep
destroy of an unrendered widget.

This only happened:

1. If using the deep destroy option [widget.destroy(true)] and,
2. If the widget was not rendered.

In this scenario, the contentBox wouldn't sit under the boundingBox,
so boundingBox.empty() didn't have any childNodes to destroy.

When rendered, boundingBox.empty() would take care of the contentBox
just fine. Also for the non-deep scenario, we'd remove(true) both boxes
independently.

Testing
-------

All library tests, including the one added for this issue pass:

✔ [Total]: Passed: 10861 Failed: 0 Total: 10956 (ignored 95)

Confirmed that the newly added test failed prior to the fix.
Fixed trailing space/long line jshint issues. No functional changes
Merge branch 'contentbox-unrendered-deepdestroy-fix' into dev-master
Build for Widget contentBox node cache cleanup.

Also contains some trailing whitespace and long line tweaks to keep
jshint happy (all the modules which aren't widget-base).

All library tests pass:
✔ [Total]: Passed: 10862 Failed: 0 Total: 10957 (ignored 95)