styling issues (ios)

[cpg]

here are some styling issues that appear to not work as expected in iOS:

1. header background with alpha being zero not respected in ios but respected in android: https://jasonbase.com/things/p88r

2. the padding of the username textfield is seemingly default to 0 if not specified in the jason, whereas in android it seems to default to some reasonable padding, so there would normally be no need to specify padding, which is a big plus to ease of use.