Refs #1485

 * Fixing wrong metadata for all plugins, cleaning up columns and ensure consistency in API (eg. VisitsSummary.get now returns conversion rate with %)
 * Adding a generic filter Truncate, updated doc at: http://dev.piwik.org/trac/wiki/API/Reference
 '''filter_truncate''' ; if set, will truncate the table after $filter_truncate rows. The last row will be named 'Others' (localized in the requested language) and the columns will be an aggregate of statistics of all truncated rows. 
 * Adding common helpers to get a "pretty" value from a given metric and column name
 * Adding new time export format that will be used in PDF reports 12:34:56 format

Refs #1486
 * a new filter, AddColumnsProcessedMetricsGoal, can be reused to easily add processed goal metrics for a given datatable. For example:
$dataTable->filter('AddColumnsProcessedMetricsGoal', array($enable=true, Piwik_DataTable_Filter_AddColumnsProcessedMetricsGoal::GOALS_FULL_TABLE));
will process all goal metrics (and per goal conv rate, rev per visit, conversions). 
When possible, only reports necessary should be loaded using GOALS_MINIMAL_REPORT or GOALS_OVERVIEW or a given idGoal 


git-svn-id: http://dev.piwik.org/svn/trunk@2594 59fd770c-687e-43c8-a1e3-f5a4ff64c105