[Website] Attachments with number sign (#) breaks link

Steps to reproduce bug
1. Open the following forum topic: http://musescore.org/en/node/8074
2. Click on the attachment

Expected behavior: Attachment should download normally:
http://musescore.org/sites/musescore.org/files/3%20Moment%20Musicals%20…

Actual behavior: Website gives a "Page not found" error:
http://musescore.org/sites/musescore.org/files/3%20Moment%20Musicals%20…

Discussion: The number sign in the file name causes problems. "#" should be escaped to "%23". (Note: this only applies to attachment links. Number signs used for linking to a particular HTML id should still be permitted for forum comments.)