Initial classpath support

Handle classpaths: add them to the top-level type index, create bound
nodes backed by classfiles, and allow types on the classpath to be
resolved during binding.

MOE_MIGRATED_REVID=133328092
diff --git a/pom.xml b/pom.xml
index d295b7e..c7596a8 100644
--- a/pom.xml
+++ b/pom.xml
@@ -79,8 +79,8 @@
         <artifactId>maven-compiler-plugin</artifactId>
         <version>3.1</version>
         <configuration>
-          <source>1.7</source>
-          <target>1.7</target>
+          <source>1.8</source>
+          <target>1.8</target>
           <encoding>UTF-8</encoding>
         </configuration>
       </plugin>