Add groundwork for heightmapped terrain.

This pr adds support for per-tile template data, and converts the minimap color, ramp type, and cell height data for the TS temperate tileset.  It also adds support for the extra sprite data in tmp(ts), and adds a widget for rendering terrain templates.

These features aren't used yet, but can be tested on my [ingame map editor](https://github.com/pchote/OpenRA/tree/ingame-map-editor) branch.

A screenshot showing where this is heading:

![editor](https://cloud.githubusercontent.com/assets/167819/4839174/5180dd92-5ffa-11e4-8309-121d4429d824.png)