The Personas can be install through oxt extensions.

The user can install an oxt extension and choose his/her theme from
the Personalization page.

* Created a template in Common.xcs registry to hold the values for the
  PersonasList set.
* Added 3 buttons to personalization_tab.ui to incorporate the latest 3
  personas installed through extensions.
* Currently, only 3 installed personas are shown alongwith the default
  available personas.

Change-Id: I30a40ae48d17f4ed8caef33854ef88afcbec5a54