Extracted the iteration over collections and creation of variable fetchers into

a pluggable component.

This allows scaling down to the GWT environment by hiding the reflection code
via GWT's super source mechanism.

And it allows scaling up to non-Java languages (like Scala) by allowing the
library client to extend the DefaultCollector and teach it about Scala
Iterators, Iterables and Maps.

I also just realized that GWT has no facilities for Reader and Writer, which is
going to complicate making things work in GWT even further. But for now, I'll
just leave things as is.

pom.xml

@@ -62,6 +62,9 @@
           <showWarnings>true</showWarnings>
           <!-- yes, those quoted spaces are a workaround sanctioned by the Maven idiocracy -->
           <compilerArgument>-Xlint" "-Xlint:-serial" "-Xlint:-path</compilerArgument>
+          <excludes>
+            <exclude>com/samskivert/mustache/gwt/**</exclude>
+          </excludes>
         </configuration>
       </plugin>
       <plugin>