Add styles for purple, blue, and black buttons.

Using Drawable 9 PNG's to allow these tooltips to stretch vertically and horizontally.

To use, just provide the style.

<Button android:id="@+id/vendor"
        style="@style/VendorButton"
	android:text="abcd"/>

![image](https://f.cloud.github.com/assets/326857/1444112/a8242f5c-41fe-11e3-9a4c-bd60506b0175.png)

Related to issue https://github.com/steffanc/Tahoe/issues/9