This is a followup to #1485
See existing functionnality in API.get* methods from the API page.
Metadata improvement list:
The final state could be that each plugin defines in their metadata the default display options for each report. We would then have to set this array of options to the ViewDataTable which would call the specific functions setColumnSorted() setColumnsToDisplay() setFooterMessage() etc.
Other UIs (like Mobile Piwik client) and other report exports (like PDF reports) could benefit from these as well, which would also ensure consistency and make Piwik reports clear to understand.
Moved "add subtable report to call to fetch subdata (eg. keywords BY search engine)" to ticket #2742