Fixed OET returning unsupported expressions

Don't dig into IEnumerables, which causes expressions that are not
supported; for example, {Resources.Item.FullName} which is not
handleable currently.
OET does not throw on unsupported expression anymore

But what it will do however, is - if desired - manually throw an
exception that gives more details. The reason is that currently,
retrieving the value from an indexer is not supported (if that will ever
be supported). Thus what we now do, is yielding an exception that is
more helpful.
Merge branch 'master' of https://github.com/chrishensel/AlarmWorkflow