Extract attachments view: Fixed contenttype helper when lookup via filename.

The `content_type_helper` used for displaying the according icon in the `type`
column of the attachments table, has a fallback for attachments with
`application/octet-stream` as contenttype.

But this fallback has not work correctly, because the `globFilename` method
always returns the mimetype itself.
Added `restore_transition` property to document and mail class.
Merge pull request #683 from 4teamwork/pg_fix_remover_tests

Added `restore_transition` property to document and mail class.
Merge pull request #682 from 4teamwork/pg_fix_extract_attachment_helper

Extract attachments view: Fixed contenttype helper when lookup via filename.
Made the AddPublicTrialColumn more robust, when value contains none JSON data.
Dropped assertion on SQL DB exception message, because the message is DB-version dependent.
Pep 8 cleanup.
Merge pull request #684 from 4teamwork/pg_fix_test_sql_task

Dropped assertion on SQL DB exception message.
Merge pull request #685 from 4teamwork/pg_made_column_adding_robust

Made the AddPublicTrialColumn upgrade step more robust, when value contains no JSON data
Revoke list folder contents permission for Administrators on repository.
Fixed test name in remover tests.
Add repository delete action and confirmation view.
Adjust global role mapping for delete objects permission.
Adjust `Delete objects` permission for repositories.

With the previous changes on the rolemap.xml the `Delete objects` permission
is not longer avaiable for Administrators. But the Administrator should be
allowed to remove repositoryfolders. Therefore we extend also control the
`Delete objects` Permission in the repository workflow.
Revoke delete permissions for dossiers

This is necessary because the repository workflow has changed so that the
Administrator role has newly the `Delete objects` permission.
Therefore aquiring the `Delete objects` permission is no longer possible.
Added monkeypatch for _verifyObjectPaste to allow moving content without delete objects permission.