[split] util-app: GlobalFlags to load only Scala object classes

Problem:

`GlobalFlags` has a discovery mechanism to find any global flag classes,
where the classpath is scanned and every class is loaded to check if it is
annotated with `GlobalFlagVisible` and if it is a Scala object class.

This discovery mechanism is an expensive operation, and it might fail if
classpath contains classes with incompatible definitions. This scenario might
happen if classpath contains different versions of the same library (e.g.
application using Guava library in a Hadoop environment).

Solution:

Instead of trying to load any class, restrict it to only Scala object class.
it will speed up the discovery, and avoid issues regarding class loading.

RB_ID=513545
[split] util-core: Fix compile error against 2.11.4 in SpoolTest

RB_ID=518073
[split] Rename Buf helpers to be Buf.*.{Owned,Shared}

Problem:

Buf.*.Unsafe and Buf.*.Copied don't properly convey the intent of these constructors. "Unsafe," in particular, serves to be more alarmist than informative.

Solution:

Rename these to Buf.*.Owned and Buf.*.Shared ot indicate the proper intent.

RB_ID=518757
[split] Fix util-app/src/main/scala BUILD file to correctly publish artifacts

RB_ID=519145
[split] util-logging: ScribeHandler publishes stats using StatsReceiver

Problem

Scribe stats are currently only logged.  The logs can be queried in bulk using tools
like loglens, only if scribe is healthy.

Solution

Expose stats in ScribeHandler allowing publishing to a StatsReceiver.

RB_ID=508411
[split] util-core: Add Java compilation tests for Buf

RB_ID=515127
[split] twitter-server: Refactor constructs around /admin

Problem

Our work towards improving the twitter-server administrator interface was
incomplete and needed a second pass.

Solution

Make the following improvements:

- Introduce a more flexible mechanism for hooking into the navigation
  pane. The com.twitter.server.Admin trait now defines a `routes` field which
  represents a collection of endpoints that the admin server will add to its
  namespace. This is combined with the global com.twitter.finagle.http.HttpMuxer
  to form the admin http Service.

- Formalize the constructs we use to build admin http endpoints. Each endpoint
  now simply extends Service[Req, Rep] and uses a collection of HttpUtils to do
  http. Mustache templating is replaced in favor of string interpolation.  This
  simplifies our dependencies and gives us more static guarantees. We could take
  this even further and define a custom interpolation that verifies xhtml, for
  example.  Finally, endpoints can be decorated with views (finagle filters)
  which wrap the returned content in an html template. Admin services
  communicate to these views via the http content-type headers.

- Better integration with Metrics. We now more thoroughly search the metric
  namespace for finagle servers and clients. The features which are dependent on
  stats are less brittle since we use the StackRegistry to extract registered
  entries for both servers and clients.

- Simplify how we generate the Summary page. Each endpoint is responsible for
  producing html fragments which are stitched together via ajax calls. This moves
  all the feature logic into Scala rather than Javascript.

- Better integration with Finagle. Client/Server parameter introspection was
  fixed and we now we display the Finagle version in Summary.

- Proper static resource loading via path names rather than http query strings.
  More robust handling of http content-type for common file types.

- Lots of UI fixes and improvements.

RB_ID=501201
TBR=true
[split] remove myself from owners

RB_ID=521835
TBR=true
[split] util-core/Duration: add *(Double) and /(Double)

RB_ID=522241
[split] Fix Scala and Java versions in Travis config

Problem

We no longer intend to support Java 6, and it should not be included in the
Travis config. Also the use of `+test` in the SBT command causes the tests to
be run against all Scala versions in the SBT config, not Travis's version.

Solution

Remove OpenJDK 6 and the plus sign in the SBT command, and add Scala 2.11.2.

Result

Tests run as intended.

Signed-off-by: Travis Brown <tbrown@twitter.com>

RB_ID=523195