fix(ngEventDirs): execute `blur` and `focus` expression using `scope.$evalAsync`

BREAKING CHANGE:
The `blur` and `focus` event fire synchronously, also during DOM operations
that remove elements. This lead to errors as the Angular model was not
in a consistent state. See this [fiddle](http://jsfiddle.net/fq1dq5yb/) for a demo.

This change executes the expression of those events using
`scope.$evalAsync` if an `$apply` is in progress, otherwise
keeps the old behavior.

Fixes #4979
Fixes #5945
Closes #8803
Closes #6910
Closes #5402