Fixes #584, #536, #2031 - Kuddos to Benaka akka capedfuzz for this great...

Fixes #584, #536, #2031 - Kuddos to Benaka akka capedfuzz for this great patch!!! I did a few minor modifications in wording and metadata output
 * Add Report "Visits by visit number" under Visitors > Engagement
 * Add Report for all Goals (including ecommerce): "Visit until Conversion": number of visits until the conversion occured
 * Add Report for all Goals (including ecommerce): "Days until Conversion": days since the first visit

Notes
 * These new reports are also in the Metadata API so should be displayed in Piwik Mobile, and can be exported in the Scheduled reports.
 * filter_only_idgoal now renamed as idGoal for consistency
 * refactored the "Beautify labels" for ranges in generic filters 
 * refactored archiving code to process multiple reports in one generic SQL query 


git-svn-id: http://dev.piwik.org/svn/trunk@5378 59fd770c-687e-43c8-a1e3-f5a4ff64c105