Fix #79: create new WordPress.com blog  from existing account

Fix #79: create new WordPress.com blog  from existing account

This adds a "Create WordPress.com site" to the preferences view and fix #79. That doesn't mean the blog management preferences are perfect, we still have to ease the way to add existing blogs from logged in WPcom users. This will be done in another branch (NUX improvements) by the blog auto-syncing feature.

![screen shot 2013-11-27 at 15 43 49](https://f.cloud.github.com/assets/40213/1632357/b823731c-5776-11e3-93eb-f3fb93681ac9.png)
![screen shot 2013-11-27 at 15 43 10](https://f.cloud.github.com/assets/40213/1632356/b6197a62-5776-11e3-8074-cef97e7ebbea.png)