Standardize which properties CustomElement.observe() reports,
regardless of whether or not browser natively supports Object.observe().

Also may inadvertently fix a bug with CustomElement#_getProps()
returning a list with duplicate entries.

Refs ibm-js/decor#17, ibm-js/decor#22, and depends on
ibm-js/decor@ae66259f04bf7e665c6666ce8ff78c058837b4ff.
architecture doc
document a11y and a11yclick
document BackgroundIframe
Container doc
CssState doc
documentation for FormWidget, FormValueWidget
HasDropDown doc
KeyNav doc
place and popup documentation
typematic doc
uacss doc
ViewPort doc
update custom elements 101
update index.md
update migration doc
doc for focus
handlebars doc: fix typo, cleanup
fix register
cleanup  theme.md to work w/jekyll and for recent theme.js changes