Custom regular expression not executed when generation source is "Generate the token from the node body"

Issue Summary

The custom regular expression for the generation source of metatags-description is not executed when the generation source is "Generate the token from the node body".

Also, the regular expression is executed only after all the HTML tags have been stripped, making it impossible to clean up items based on CSS class name etc.

Attached is a patch.

Note that the problem with when the regular expression runs still exists for "Generate the token from teaser" in this diff. I believe the regular expression match should be moved before the tag stripping in the other part of the logic as well but wanted to keep the diff small.