Restricting the receipt API to authenticated users (bug 917601)

Otherwise a 500 will be raised given the usage of `request.amo_user`
don't run files languagepack tests twice
Merge pull request #1159 from davidbgk/917601-receipt-api-500

Restricting the receipt API to authenticated users (bug 917601)
Allow collection images to be deleted (bug 917081)
Merge pull request #1170 from chuckharmston/917081-clear_image

Allow collection images to be deleted (bug 917081)
Removed unused webapp indexing code from AMO (bug 918947)
Added term query for exact match boosting (bug 880295)
add "privileged" to "app_type" for search API
file_create invokes get_localepicker in a signal, so move mock back up a level