some improvements (fixes login for gmail)

Hi!

Changes included in this pull request:

* some formatting changes to comply with Apple's guidelines (you can ignore those if you want)
* adds spinner to show while the webview is loading (so you don't stare at a white screen)
* adds some DEBUG fences around some debug logs, to reduce noise in the console
* allows loading of external requests inside the webview, to fix the gmail (and some other external providers) login
* adds a way to customize the body format when verifying the assertion