Basic funnel data logging for UploadWizard

See also https://meta.wikimedia.org/wiki/Schema:UploadWizardStep

Change-Id: Ifc79d45617f1712ad937373cd51592bfea645e4c
Mingle: https://wikimedia.mingle.thoughtworks.com/projects/multimedia/cards/609
Merge "Basic funnel data logging for UploadWizard"