Remove checks for SDK versions older than our target SDK
Removes conditional code for older Android versions (IceCreamSandwitch, JellyBean, KitKat, Lollipop) since we no longer support Android older than Lollipop (5.0).
This doesn't remove KitKat support in the SFTP plugin since it's a bit more convoluted. It will be done in a separate MR.
Edited by Albert Vaca Cintora