Refs #472 New metrics: Average Event value, Number of events with value.

plugins/Events/API.php

plugins/Events/Archiver.php

plugins/Events/Events.php

plugins/Events/lang/en.json

...ts_Events.getAction_lastN__API.getProcessedReport_day.xml

..._Events.getCategory_lastN__API.getProcessedReport_day.xml

...ents_Events.getName_lastN__API.getProcessedReport_day.xml

...tion/expected/test_CustomEvents__Events.getAction_day.xml

...on/expected/test_CustomEvents__Events.getAction_month.xml

...on/expected/test_CustomEvents__Events.getCategory_day.xml

.../expected/test_CustomEvents__Events.getCategory_month.xml

...ration/expected/test_CustomEvents__Events.getName_day.xml

...tion/expected/test_CustomEvents__Events.getName_month.xml

...Events_eventCategoryOrNameMatch__Events.getAction_day.xml

...ents_eventCategoryOrNameMatch__Events.getCategory_day.xml

...omEvents_eventCategoryOrNameMatch__Events.getName_day.xml

...s_segmentMatchesEventActionPlay__Events.getAction_day.xml

...segmentMatchesEventActionPlay__Events.getCategory_day.xml

...nts_segmentMatchesEventActionPlay__Events.getName_day.xml