update ve extension to send api uri instead of prefix
generalize apiUrl helper to apiSource, supports both prefixes and config endpoints
@kflorence you happy now?
Merge pull request #1922 from Wikia/VE-540-parsoid-php-api-update

VE-540 Update VE PHP controller to send API URIs
adding qqq
Remove wgVisualEditorParsoidPrefix
Merge branch 've-sprint-6' into VE-553