[split] Dtab: make Dtab.base changeable, fix RefineryTest

This may be a temporary change; it makes integrating with non
twitter-server systems much simpler.

RB_ID=231543
[split]  Moving warmup filter from timeline service to finagle-exp

RB_ID=229069
[split] Avoid creating a new 'NoStacktrace' array for each exception.

RB_ID=233687
[split] Finagle: val up a few more constant `StatsReceiver.scope`s and `.counter`s

RB_ID=231399
[split] finagle-testers: small latency evaluation framework

RB_ID=231287
[split] COORD276: Make coord-team the owner of zk code.

This adds the coord-team to the GROUPS files in
util/util-zk/GROUPS
util/util-zk-internal/GROUPS
finagle/finagle-serversets/GROUPS

RB_ID=235085
[split] finagle: fix a tag breaking scaladoc

`<address>` is preserved as an HTML tag in Scaladoc, causing
non-well-formed HTML output.

RB_ID=237341
NO-QUEUE=true
[split] finagle-docs: fix changelog

RB_ID=237339
[split] finagle-(stress|ostrich4): deprecated Netty methods

`DefaultHttpMessage` deprecated (get|set)Header methods.  Use
`.header.set|get` instead.

RB_ID=237349
[split] finagle & util: 2.10 pattern matching strictness

2.10 compiler is much more strict about pattern matching exceptions and
warns if catch all case is not qualified with `Throwable`.   So let's do
that to decrease compiler warnings.

RB_ID=237379
[split] StabilizingAddr: Proper passthrough.

RB_ID=234977
[split] finagle-core: moved mask cancel filter over to Future.mask, moved from specs => scalatest

RB_ID=222007
[split] Initial ConfigBus client and server checkin

RB_ID=222471
[split] finagle & util: sbt version in `build.properties'

Although we provide a script to download sbt, people will continue
trying to compile util and finagle with their sbt installation.  Add a
build.properties file to specify the sbt version we're using so it
doesn't cause them problems.  This is also helpful for cases where our
'./sbt' also fails with "Error during sbt execution: No Scala version
specified or detected" message.

Update ./sbt scripts to download 0.12.4 (latest 0.12).

Rework script:
- Remove unused code
- Check SHA1 instead of MD5
- Suggest deleting and running ./sbt again if checksum doesn't match
- Silence curl spam; print the nature of error.

RB_ID=238259
NO-QUEUE=true
[split] twitter-server-internal: Default Dtab, and a hooking mechanism Install a default Dtab for twitter-server-internal users. We expose an API to install the Dtab for projects that do not yet use the twitter-server-internal directly.

A new flag, -dtab.add, is exposed to add entries to the
base dtab. This may change to expose the entire base dtab.
Note that even without this support, one can effectively install
a new base dtab by adding -dtab.add ???/->fail!,..???

During testing, I also discovered that the current ServerSet
implementation may throw an exception on permissions failure.
(This seems bad: watching a serverset should be a read-only op.)
I???ve worked around this by a fixed retry mechanism. The real fix
is ServerSets2, which does not attempt to create ZK directories.

RB_ID=234989
[split] bump util to 6.9.1-SNAPSHOT

RB_ID=242923
TBR=true
[split] bump finagle to 6.9.1-SNAPSHOT

RB_ID=243851
TBR=true
[split] fix sbt build

RB_ID=244505
TBR=true
[split] Tagging flaky ZookeeperServerSetClusterSpec test

RB_ID=244421
TBR=true
Merge branch 'tmp'