Localization, and introducing es-MX

With this release we bring in i18n, and support for es-MX. Specific highlights below. In addition, we've improved the connection with Vioscreen for FFQ hand off, expanded activation code support, and laying the groundwork for modeling FFQ data locally

• i18n general (text/sorting/translation support/language tweaks/emails): #325, #329, #339, #341, #342, #348, #349, #350
• Pass off weight/height/language to vioscreen and FFQ selection: #301, #331, #332, #335, #351
• Avoid null answer models on pulldown: #333
• Restoration of existing vioscreen <-> barcode associations: #297

Thank you in particular to @cassidysymons, @dhakim87, @Oliver-Nizet and @gwarmstrong for work on this release.