Issue #178 - Hide advanced options in EncryptActivity

This is a commit trying to fix issue #178.

For now I've made the Show/hide advanced settings button as a text only button in order to not over clutter the UI. If you prefer to have a button instead of a text, I can also do that :) 

Let me know if this seems ok.

// I really like this project and I would like to participate in GSoC 2014