#6 unique auto completion hits (state: open)

Description

If more than one attribute is selected for auto-completion, hits are output multiple times. This changes makes hits unique.

Checklist

• Read and understood the CONTRIBUTING guidelines
• Created tests, if possible
• All tests passing
• Extended the README / documentation, if necessary
• Added myself to the @authors in touched PHP files
• Checked the changes with phpcq and introduced no new issues

LGTM

Found better solution to prevent for multiple hits

@Ainschy pls fix the header lines - see my comments...