Fix ti.ui.iconbutton for Android

Hi Javier!

I have 3 modifications from your project:
- When I run the app on Android, I has 2 alerts for XML tags not closed
- It's more simple to use ti.ui.defautunit to DIP for the demo app (to small on XHDPI screen when you use pixel unit)
- Fix the ti.ux.iconbutton widget for Android with just 1 properties on TSS

For the ti.ux.iconbutton widget, I added a default color because for iOS, default color is blue and for Android is grey...But I'm not sure if it's the right place for define the default color.

What do you think about this ?

Thank you. Damien