#307287: (Panels related) view::preview() would override previously set arguments if no arguments were sent.

#319167: add_table() would return TRUE if the table was already added but the expected return is the alias.

#317803 by pwolanin: Change message and link for advanced help module whining if module is present but not enabled.

Since it's not easily possible to do the views filter block externally, bring the functionality directly into Views, including modifying the ajax for that to work.

query::add_field() called ensure_table too aggressively and could cause aliases to improperly overwrite already existing tables.