Improved generateNullCheckForExpression (don't check the same thing more than once)

Also, some annoying whitespace changes.
Improved text interpolation (don't call setter for variable name more than once)

Fix for EventManagement.on() mixin not working.
Updates for different null-checking in BuildTools.
Add full type annotations on public APIs

This is to assist code completion.  Also:

* renamed "query" to "collection" in local vars / fn params
* removed some unused classes (DtxLayoutTools, Animation)
* minor code cleanup (and bug fix?) for dtx.single.Traversing.parent()
Use type parameters for collection functions that return the original collection.

This means if you are using something that extends a collection, like a widget, the return object keeps it's original type information, menaing that chaining can include functions specific to that widget, not just the generic collection functions.
More type hints. Use `array.indexOf` instead of `Lambda.has`
Add documentation for ElementManipulation helper classes

Includes minor fix-ups that I noticed while going through things.
Add documentation for style class.  Minor cleanup and fixes also.
Get rid of clone(deep) api, just use clone()

Also, minor cleanup of textContent() in XmlWrapper
Add code documentation for Detox module
Minor test change
Added documentation for EventManagement helper classes.

Also removed the "ready" function.  Detox.ready() is where it's at.
Add documentation for `Traversing` helper classes.

Also refactor `ancestors` to use loops instead of recursion, and a few other small cleanups.
Fix for importing of files from local context
Add getStyle, removeCSS. Fix setCSS, hide, show.
Add documentation (and minor fixes/cleanups) for DOMManipulation classes
More null check fixes for static platforms
Update release notes, bump to RC.2
Prevent null check generating `null != null` checks and breaking things.
Change dtx-show and dtx-hide to use `Style.show()` and `Style.hide()`
Let show() and hide() have a sensible fallback on non-JS platforms

Instead of having no effect, get them to add or remove the "hidden" class.
Later getting it to intelligently read and write the "style" attribute might be a good move.