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.
Rewrite Elasticsearch AsciiDoc chapter

Reorganized and expanded to cover the new
index.search.interface=... configuration approach to ES alongside the
old legacy ES configuration settings
Tweak AsciiDoc admonition block styles
Tweak ES INDEX_DIRECTORY handling, config tests

ES now just checks whether the config has an explicit value for
INDEX_DIRECTORY instead of checking whether any of the path.data,
path.work, and path.logs settings are present.

Adding some new test cases to exercise Elasticsearch data/work/logs
directory configuration behavior described in the docs.
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.
Expand and edit ES manual page

Adding new section on connecting Titan and secure Elasticsearch
clusters, updated many existing sections, including legacy-track
config examples, descriptions of interface-track config options, and
troubleshooting connections to remote ES clusters
Update descriptions on two ES ConfigOptions
Separate ES node/transport-specific options

Now TTL_INTERVAL is only considered by the Node client, and
CLIENT_SNIFF is only considered by the transport client
Documentation: add prev/next links to header

Both the fixed header and the floating/sticky header now have
chapter-previous and chapter-next links.  These links complement
rather than replace the existing links just above the copyright
footer.
doc CSS hack: make anchors offset by header height

Using intra-page anchor links with the documentation prior to this
commit was sort of clumsy, since the sticky/floating header at the top
of the viewport would obscure about the topmost ~85 pixels of whatever
the link jumped to -- usually the section header and an initial
sentence or two.

This CSS hack makes anchor links jump about 88 pixels too high to
compensate for the height of the floating/sticky header.
Update introductory Elasticsearch quote

The old quote is no longer listed on the ES homepage, so the
attribution link has rotten.  Updated with a similar (but current)
quote from the ES overview page.
Typos and prose edits in ES doc page
Update ES ConfigOption descriptions