Remove the reset_properties() methods

These methods were added only for unit tests, but cleaning up the
properties and the surrounding environment is more easily handled in the
tests responsible for the changes.

Also fixes a bug in resetting WP_SEO::formatting_tags where missing tags
wouldn't be removed from the array once added.
Add set_options() method and update get_option()
Move nonce verification into separate conditionals

Allows us to see more specifically why verification failed, particularly
in testing.
Mark some methods as @codeCoverageIgnore
Spit and polish
Update phpunit.xml for code coverage reports
Clean up setUp() and tearDown() in formatting-tags tests
Clean up docs and vars in formatting-tags tests
Add tests for formatting-tag descriptions
Add a test for the excerpt tag's generated excerpt
Test the author tag's use of get_the_author()
Add a missed _has_description() test
Organize the tests for per-object fields
Clarify and clean up the class properties tests
Clean up the option-sanitizing tests

Removes an unnecessary setUp() and a seemingly useless test.
Improve tests for arbitrary meta tag output
Clean up wp_title() and wp_head tests
Add a meta test and a test for returning an original title
Add metabox tests: registering, rendering, saving
Add tests for the settings page, fields, and text