Add Google+ color constants.

Found by google search.

The plan is to extract color and dimension information into style.js.
main.qml: Set entire background to one color.

The rectangle is not redrawn if I resize the window. Haven't figured out how to
get access to a resize() signal or application.dimensions property.
Adjust colors and sizes for  text boxes.
Use word wrapping for all text boxes.
Add margins around the input text box.