Ensuring that disallowed types do not show up in search results

* There is a bug in the features export for apachesolr search
  that doesn't respect the types that shouldn't be indexed. This
  will ensure that those types don't show up in search.
Making PR fixes

* Fixing incorrect node type name for campaign_group
* Changing true to TRUE
* Renaming allowed_search_types variable
Merge pull request #3327 from blisteringherb/search-exclude-types

Ensuring that disallowed types do not show up in search results