Prevent upload and show error message if source upload filename has a semicolon.

    Zanata cannot accept files with a semicolon for upload due to a bug in
    seam taglib that causes filename truncation. This prevents the upload
    from the browser to avoid the confusing truncation behaviour.
move error string to messages.properties
Merge pull request #94 from zanata/stop-semicolon-upload

Prevent upload and show error message if source upload filename has a semicolon.