Disable iOS for now

[baltpeter]

Given the difficulties with hosting iOS devices for analysis, we have decided to disable iOS for the initial launch and only support Android for now. But since we do want to reenable iOS support at some point, I've tried to be minimally invasive with the changes so they can easily be reverted in the future.

A few things to note:

• I have deliberately not given much thought to the design changes on the homepage, since that is a separate TODO item.
• In the current implementation, all search results lead to the (very stub-y) "app details" page. Again, I deliberately didn't spend a lot of time on this since I feel we need to have a discussion as to what the flow should be here (@zner0L, you mentioned in evaluate-response should be a single form with options #13 that you were startled by the analysis starting immediately).