Cleanup and fix filesystem.xml assembly

* Deleted two identical copies of the filesystem.xml assembly
  descriptor.  Instead of having separate copies,
  titan-dist-hadoop-{1,2} now share a single one that lives in their
  common parent.

* Made -Ddev.hadoop=2 the default again.  Just prior to this commit,
  neither the hadoop1 nor 2 version of the filesystem.xml assembly
  activated by default, so no (reporoot)/bin, lib, conf,
  ... directories would be created by default.  We've been building
  these directories by default for a while, so that behavior has been
  restored.
Merge branch 'titan05' of github.com:thinkaurelius/titan into titan05
Belatedly adding filesystem.xml

I think this should have been part of
ca904c6c598fbbe7c7101d201cbb225d2b9fdf36
Tweak ES manual chapter intro and options section
Rewrite ReflectiveConfigOptionLoader

This is now optimized for the case where only standard Titan config
options are in use (no third-party options), but falls back to a
slower implementation that can find third-party options if it fails to
resolve an option.

It's also got methods that support completely disabling it, in case
the user wants to takeover config option initialization, and for
configuring the classloader chain that it uses.  The default
classloader chain is

* ReflectiveConfigOptionLoader.class.getClassLoader()
* The current thread context class loader
* The classloader of the calling class

But this can be overridden through public methods at runtime.
Add test that disables config option loader
Simplify ConfigurationPrinter use in titan-dist

Now that ReflectiveConfigOptionLoader deals with the classpath
changing at runtime, titan-dist can invoke ConfigurationPrinter with
exec:java instead of exec:exec
Deleting commented reflection code
Classloader configuration tweak

ReflectiveConfigOptionLoader has two different paths for loading
config options.  The fast path is tried first, but it only finds
options in a hardcoded set of standard Titan classes.  The slow path
finds anything with a runtime-rentention annotation.  The fast path
already supported a user-configured classloader chain, but the slow
path did not.  Now the slow path supports the same user-configured
classloader chain.