Improve Exception Reporting

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• #368 by @jankapunkt — closed without merging

Currently in Kadira we get lots of exceptions that look like this:
[client] Exception in tempalte helper:

As there is no more detail they all get grouped together which can be painful to wade through.

One simple update we could make in Blaze is to pass the name of the helper function to _wrapCatchingException (in lookup.js) so
```
return Blaze._wrapCatchingExceptions(f, 'template helper').apply(self, args);
```
Would be instead something like
```
return Blaze._wrapCatchingExceptions(f, `template helper ${templateFunc.name}`).apply(self, args);
```
It would be even better if we passed the actual template name into wrapHelper and then we could report that too meaning a unique grouping by template name and helper in Kadira or whatever other error handling program someone is using.

I'm happy to make the PR if whoever monitors this agrees :smiley:

Start in lookup.js, focusing on wrapHelper and _wrapCatchingExceptions, then review the closed linked pull request #368 for prior work. Determine how helper and template names can be included in exception reports so different helpers group separately in Kadira or other error handlers; the issue is done when that context is reported consistently.

Written by the indexing model from the issue text.