Proper handling of strings description of data (report titles, legends, date handling)

[mattab]

A report is defined by its data, but this is not enough.

We also need to somehow define in the report
- a date format (for graphs it may be ‘Week 2’ but when displayed in the UI it would be ‘Week of January, 21st’)
- legends for graphs (eg. ‘%s visits’ or ‘%s distinct keywords’)
- title for the report (eg. ‘Distinct keywords’ ‘Countries’)
- titles for graphs (eg. ‘Evolution of the number of %s’, or simply use the report title as is)
- existing bug, in Visitors > Overview, the graph always shows the english word ‘days’ eg. in french: volution sur les 30 derniers days
- other..?

Also see #5546

This has to be specified first as I think I may have forgotten some points.

[mattab]

- all graphic showing data evolution are labelled with the text "nb_uniq_visitors"
no matter if youre watching last visits graph, global visits graph or any other.
Its happening in every graph under Visitors subpages and in the Dashboard.
- In Referers->Evolution page, in addition, I think its melting titles because I read
in spanish "Entrada directa nb_uniq_visitors" for the first graph,
"Paginas web nb_uniq_visitors" for the second and so on.

[mattab]

(In [1072]) - API CHANGE: the API for the function Piwik_AddWidget has changed. The new API is Piwik_AddWidget( $widgetCategory, $widgetName, $controllerName, $controllerAction, $customParameters = array()). See examples of calls in all the core Piwik plugins. This change was necessary to make widgets more modular (they now accept custom parameters).

• API CHANGE: a small number of CSV outputs for some API calls would change following the simplification of DataTable_Simple implementation. Affected calls are VisitsSummary.get, Goals.get, VisitFrequency.get. This is due to a change in the implementation of DataTable_Simple (we simplified implementation).
• FIXED Event System refactor #84 Added proper translations for all columns, in tables, and graphs.
• FIXED Visitor interface implementation. #322 piwik is now using open flash chart 2
• FIXED Viewdata cleanup #126 all dates should be correctly displayed in all graphs. For example, evolution graph for days would show, on the X axis "Mon 29", "Wed 31". For months it would show "Aug 2009", etc.
• ADDED: when hovering any of the sparklines, the UI makes it clear that clicking will refresh the evolution graph. This feature was in Piwik for months, and even Google Analytics implemented this UI feature after Piwik. However in Piwik it wasn't clear to the user that the sparklines were clickable.
• ADDED: now widgets can be created with custom parameters. This makes it possible to create a widget that calls a controller->action with other custom parameters, this is used in Piwik to draw an evolution graph (module=VisitsSummary & action=getEvolutionGraph) for a given metric (&columns[]=nb_visits). These custom parameters are automatically forwarded to the sparkline url, the flash graph when clicked on sparkline, etc.
• The widget layout is now saved as a JSON string rather than a custom data structure. The dashboard code should be able to read & restore most of the layouts from the old format (except the evolution graphs widgets). Simplified the Dashboard.js, widgetMenu.js, cleaned up what was a messy code.
• Added sentence in Widgetize to let users know they can easily export the Piwik dashboard in an iframe.
• Changed the way translations used in Javascript are loaded: all translations strings finishing by _js will be loaded to be used in the templates when calling {loadJavascriptTranslations plugins='YOUR_PLUGIN_NAME'}
• Moved all templates in plugins under plugins/$PLUGIN/templates/
• 'Khtml (Konqueror, Safari)' now displayed as 'KHTML (Safari, Chrome)'