feat(directive injector): DiCircularDependencyError -> CircularDependenc...

[vicb]

...yError

And make CircularDependencyError extends di.CircularDependencyError
so that catching di.CircularDependencyError catches any circular dep
error

/cc @rkirov @jbdeboer

[vicb]

@rkirov I've further modified the PR (and remove the LGTM status):

• It's a pain to have CircularDependencyError defined in two different libs, you have to disambiguate each time you use such a type. I've renamed the directive injector one to _CircularDependencyError because it is not intended to be used directly but by using the original di CircularDependencyError
• I've updated the test to assert that the exception thrown is an instance of CircularDependencyError which is all what this PR is about
• I have tweaked the _CircularDependencyError error message to look like the one from CircularDependencyError
• I have made some variables private

Could you please take an other look ?

[vicb]

@rkirov the PR should be really ready now (the where closure has been updated)

[jbdeboer]

@mhevery It looks like the labels script is buggy, as this PR has both action:review and action:merge. I've removed action:merge manually.