Update and improve ordering language in documentation.

The intro to ordering didn't mention the order argument, likely it was written
before the option was added. This CL moves all the language into the ordering
section and improves the conciceness of the information.

Author: vitiral

src/main/java/org/junit/Rule.java

@@ -15,13 +15,7 @@
  * The {@link org.junit.runners.model.Statement} passed
  * to the {@link org.junit.rules.TestRule} will run any {@link Before} methods,
  * then the {@link Test} method, and finally any {@link After} methods,
- * throwing an exception if any of these fail.  If there are multiple
- * annotated {@link Rule}s on a class, they will be applied in order of methods first, then fields.
- * However, if there are multiple fields (or methods) they will be applied in an order
- * that depends on your JVM's implementation of the reflection API, which is
- * undefined, in general. Rules defined by fields will always be applied
- * after Rules defined by methods, i.e. the Statements returned by the former will
- * be executed around those returned by the latter.
+ * throwing an exception if any of these fail.
  *
  * <h3>Usage</h3>
  * <p>
@@ -65,8 +59,11 @@
  *
  * <h3>Ordering</h3>
  * <p>
- * You can use {@link #order()} if you want to have control over the order in
- * which the Rules are applied.
+ * You can use {@link #order()} (default = -1) if you want control over the order in which the
+ * Rules are applied. Rules with the lowest {@link #order()} value will be applied first. If
+ * multiple rules have the same {@link #order()} then those implemented as methods will be applied
+ * before those implemented as fields, with the ordering within groups dependant on your JVM's
+ * implementation of the reflection API (generally undefined).
  *
  * <pre>
  * public class ThreeRules {