Remove Unused Styles

The styles for v11 and v14 are the same as the base. Removing them as
they don't need to exist.
Add New AlertDialog Style

Adding a new style for use with AlertDialog. This sets a property so
that the text is readable on older Android versions.

The method used for the AlertDialog building is described at
http://blog.andromo.com/2011/fixing-text-colours-on-an-alertdialog-when-using-theme-light/

fixes #31