Rewrite event extension to be clearer and better factored.

Add and refactor with getComputedState,
setupCheckIfNeeded, teardownCheckIfNeeded, and
performCheck.

Replace abbreviations with English: ns, m, evt,
$t, dat (to attr), nsDat, nsLog (refactored out).

Dasherize data names. Refactor getting state to be
more DRY, which required renaming hlf-hover-intent
property to hlf-hover-intent-intentional.

Refactor and improve logging. Also use it to
obviate some of the inline comments.

Minor white-spacing and reformatting.
Reorganize styles and scripts to fix Groc task.

Groc doesn't differentiate by file extensions, so
having styles and scripts share a directory means
only the doc for the last file parsed gets kept.

Also ensure Groc only parses the source files and
not any built files.

Also minor docs white-spacing.