Do not serve PHP files from public issues directory

- These are attachments, and should not be parsed and executed!
Merge branch 'hotfix/attachments' into develop

Do not execute PHP files in the public issues directory; these are attachments.
Move archived issues to bottom of issues page

They aren't as important as the active issues list, so should be at the
bottom.
Merge pull request #91 from akrabat/issues1

Move archived issues to bottom of issues page
Merge branch 'hotfix/91' into develop

Close #91