VE-1555: Do not "double fire" tracking for performance.system.activation/edit-page-ready

Use "wikitext" property on target object as a flag to figure out if it's "initial" load of VE (then track event) or subsequent (then do not track event)

https://wikia-inc.atlassian.net/browse/VE-1555
Merge pull request #4905 from Wikia/VE-1555

VE-1555: Do not "double fire" tracking for performance.system.activation/edit-page-ready