Adding FreeOTP

FreeOTP is an open-source OTP/TFA app for iOS/Android provided by Red Hat/Fedora.

If it is okay to add FreeOTP to the list, I can make the extra commit of adding the icon too.
Adding FreeOTP icon.

Based on:
https://fedorahosted.org/freeotp/browser/android/res/drawable-ldpi/ic_launcher.png

Cropped 1 transparent pixel from each side, reducing from 36x36 to 34x34.
Enabling the icon

I forgot to uncomment the icon.
Merge branch '552', closes #552