TOS/PP updates for B2G/Firefox OS Marketplace

* On mobile devices, show the RP TOS/PP below the Persona TOS/PP on the authentication page.
* On mobile devices, show the RP TOS/PP below the email list on the email picker page.
* When signing into Marketplace on a mobile device, hide the RP info at the top of the screen.

fixes #3413
Merge pull request #3418 from mozilla/issue_3413_b2g_tos_pp

Issue 3413 b2g tos pp