Create Handlebars environment through proper means
Update precompiler for new format
Remove custom template override

The isTop flag will be added to Handlebars itself so this override may be removed.
Update missing helper semantics

Matches the new parameter passing style implemented in Handlebars 2.x.
Update compiler revision check
Update handlevars package dependencies to 2.0
Update Handlebars assert message
Make Handlebars error message more informative.
blockHelperMissing now receives the proper arguments.
Update auto-published files.
Add CHANGELOG entry.
Merge pull request #9359 from rwjblue/handlebars-2-0

Update to Handlebars 2.0.