[MRM-1762] Upload Artifact page allows to uploading SNAPSHOT versions to non snapshot repositories

git-svn-id: https://svn.apache.org/repos/asf/archiva/trunk@1542152 13f79535-47bb-0310-9956-ffa450edef68
better file extension

git-svn-id: https://svn.apache.org/repos/asf/archiva/trunk@1542153 13f79535-47bb-0310-9956-ffa450edef68