Coords.php:
UniSim.php:
-Added a few more vector arithmetic test cases.

file:a/Coords.php -> file:b/Coords.php
```--- a/Coords.php
+++ b/Coords.php
@@ -1,8 +1,7 @@
<?php
-abstract class Coords {
-	// This is a stub that may contain functions or parameters that apply universally to all coordinate systems,
-	// but may never be instantiated itself.
-
+abstract class Coords {
+	// Vector math only actually makes sense in Cartesian, so we have to
+	// convert there, and convert back.
\$class = get_class(\$this);
\$vector1 = \$this->convert("CartesianCoords");

```
file:a/UniSim.php -> file:b/UniSim.php
```--- a/UniSim.php
+++ b/UniSim.php
@@ -4,15 +4,15 @@
require_once("Coords.php");

\$universe = new SpaceNode("universe node", 0, new SphericalCoords(0,0,0), null);
+echo \$universe->describe();

\$node1 = new SpaceNode("node1", 40, new LinearCoords(40), \$universe);
-
-echo \$universe->describe();

\$infra_list = \$universe->get_infra_list();
foreach (\$infra_list as \$infra) {
echo \$infra->describe();
}
+echo \$universe->describe();

\$vector1 = new SphericalCoords(5, M_PI/4, M_PI/8);
printf("Vector1: %s\n", \$vector1->string());
@@ -20,7 +20,11 @@
printf("Vector2: %s\n", \$vector2->string());