Various D8 issues

Hi,

I've been using the D8 dev version as of 98802b1944912043f743193d51dc5e7c54dbd0b0 and seem to have uncovered a few issues:

The most serious error is this:

* The regex passed into preg_match() does not contain the start or end delimiter, so preg_match() fails and produces a warning. The regular expression never matches.

Some other fixes are:

* On form validation the form element is passed into FormState::setErrorByName() which requires a string, not an array element. This leads to the name or mail field not being highlighted as an error.

* When saving a expiration as permanent when they rule is re-edited the permanent checkbox is not checked.

* #machine_name 'exists' option uses a non-existent class name (missing an 's')

* PHP notice generated as UserRestrictionsListBuilder::buildRow() signature does not match EntityListBuilder::buildRow()

I've attached a patch which resolves these issues and the module now functions OK for me - the email addresses I add to the blacklists are prevented from registering. I've not done any extensive testing so far but this seems to get me up and running.