Access to root context in partials and helpers

There is already a related bug about getting parent context inside a partial called from within a block helper: issue #182. However, tracking parent context is probably not enough - add in another block helper (e.g. an if inside an each) and things quickly get out of hand. 

The same story with helpers - it's easy enough to get current context via this, it's easy enough to pass in parent context via ".." - but once again, very quickly it becomes "../../../.." There is a hack proposed in issue #245 but I had mixed fortune with it.

The above two problems seriously affect code re-use - one must always keep track of context and nesting. There are pull requests for parentContext by introducing helpers and passing explicit parent context. While I find that useful, I also need the global context - just a couple of sample use cases: localization (must know which language to use), changing some item layout/details based on user status (essentially access check, although some might argue this is "logic" and should thus not be done inside a template).

It would be great to have access to global/root context at all times - inside an {{#each}}, inside an {{#if}}, inside any helper that I create myself and naturally inside any partials that may be nested inside block helpers.