Fixed a cache problem by duplicating the layout stack when caching it. Otherwise the reference is shared between caches and we can end up rendering too many layouts.
Several partials view directories & template options

- Allow to configure several directories for partial views
- Add a method ‘updateTemplateOptions’ to update the templateOptions
Had lost caching fix with merge
Merge branch 'feature/nested-layouts' into feature/nested-layouts2

Conflicts:
	example/app.js
	example/views/layout/default.hbs
	example/views/layout/veggie.hbs
	lib/hbs.js
Merge branch 'feature/nested-layouts2'

Conflicts:
	example/app.js
	lib/hbs.js