Rewrite core extension to be clearer and more optimized.

Most of the work was in rewriting createPlugin.
Also refactor dependent scripts accordingly.
Details follow.

Rename and optimize naming helpers: _evt -> evt,
_dat -> attr. Dasherize data property names.
Rename hlfIsActive -> hlf-tip-is-active.

Rename (_)log -> debugLog. Optimize away _nsLog.
Make log namespace the default, by convention.

Improve clarity, rename: ns, opt, $ctx.

Optimize by using _.memoize for all custom
toString functions.

Also fixup 791241d by restoring event extension
debugLog dependence on its own debug level.

Minor white-spacing and reformatting.
Simplify event extension indentation.
Refactor event extension with triggerEvent.