Investigate and fix PDF export errors

I'll will try to summarise here the errors that appear in the logs when exporting pages or spaces to PDF. Please feel free to add to this list.

• [WARNING] table-layout=auto is not supported, using fixed!
• [ERROR] At least one of minimum, optimum, or maximum IPD must be specified on table.
• [ERROR] Error while creating area : Error while recovering Image Informations (file:/confluence/images/icons/rss.gif) : \confluence\images\icons\rss.gif (The system cannot find the path specified)
• [ERROR] Unknown enumerated value for property 'relative-align': baseline
• [ERROR] Error in relative-align property value 'baseline': org.apache.fop.fo.expr.PropertyException: No conversion defined
• [ERROR] property - "font" is not implemented yet.
• [ERROR] property - "background" is not implemented yet.
• [ERROR] Error in margin-top property value '0px font-size: 12px': org.apache.fop.fo.expr.PropertyException: illegal character
• [ERROR] Error in margin property value '0 0 0 36px color: rgb(102, 102, 102)': org.apache.fop.fo.expr.PropertyException: illegal character