#385 — remove modal activity indicators from NUX

Issue https://github.com/wordpress-mobile/WordPress-iOS/issues/385

All modal activity indicators were removed with the exception being NewAddUsersBlogViewController. This view will be removed from the NUX in this issue: https://github.com/wordpress-mobile/WordPress-iOS/issues/538

Before vs. after

![modal](https://f.cloud.github.com/assets/3904502/1576591/09d69c16-515f-11e3-8040-61fca51ac7fd.png)