ExampleWidget sample page improvements, refs #236
Handlebars: better handling for duplicate bind variables.

For example, expressions like "Hello {{name}}.  How are you {{name}}?"
or {{this.x < 0 ? Infinity : this.x}}.

In this case, generate an if() like if("name" in props) rather than
if("name" in props || "name" in props).
fix templates build, fixes #240
make has.add() test not crash on node, fixes #241
Doc updates including changes related to Stateful API changes, fixes #239
use absolute MID for global.css, fixes #242
forgot to check in DialogUnderlay less files
Fix for gh-pages build error.
cleanup of register doc
general documentation about widgets
reference doc for delite/CustomElement
prepare for 0.1.9 tag
Make loading page level CSS opt-in, fixes #243.

Moved CSS like .d-popup to common.css.  Page level CSS (for body color, font etc.)
remains in global.css but global.css is no longer loaded by default.
Common.css is loaded by default instead.
prepare for 0.1.10 tag