add jaeger support, link hot container & req span (#840)

* add jaeger support, link hot container & req span

* adds jaeger support now with FN_JAEGER_URL, there's a simple tutorial in the
operating/metrics.md file now and it's pretty easy to get up and running.
* links a hot request span to a hot container span. when we change this to
sample at a lower ratio we'll need to finagle the hot container span to always
sample or something, otherwise we'll hide that info. at least, since we're
sampling at 100% for now if this is flipped on, can see freeze/unfreeze etc.
if they hit. this is useful for debugging. note that zipkin's exporter does
not follow the link at all, hence jaeger... and they're backed by the Cloud
Empire now (CNCF) so we'll probably use it anyway.

* vendor: add thrift for jaeger

vendor/git.apache.org/thrift.git/build/cmake/README.md

@@ -0,0 +1,60 @@
+# Apache Thrift - CMake build
+
+## Goal
+Extend Apache Thrift's *make cross* approach to the build system.
+
+Due to growing the field of operating system support, a proper executable
+and library detection mechanism running on as much platforms as possible
+becomes required. The other aspect to simplify the release process and
+package generation process.
+
+As nice side benefit of CMake is the generation of development environment
+specific soultion files. => No solution files within source tree.
+
+
+## Usage
+just do this:
+
+    mkdir cmake-build && cd cmake-build
+    cmake ..
+
+if you use a specific toolchain pass it to cmake, the same for options:
+
+    cmake -DCMAKE_TOOLCHAIN_FILE=../build/cmake/mingw32-toolchain.cmake ..
+    cmake -DCMAKE_C_COMPILER=clang-3.5 -DCMAKE_CXX_COMPILER=clang++-3.5 ..
+    cmake -DTHRIFT_COMPILER_HS=OFF ..
+    cmake -DWITH_ZLIB=ON ..
+
+or on Windows
+
+    cmake -G "Visual Studio 12 2013 Win64" \
+    -DBOOST_ROOT=C:/3rdparty/boost_1_58_0 \
+    -DZLIB_ROOT=C:/3rdparty/zlib128-dll \
+    -DWITH_SHARED_LIB=off -DWITH_BOOSTTHREADS=ON ..
+
+and open the development environment you like with the solution or do this:
+
+    make
+    make check
+    make cross
+    make dist
+
+to generate an installer and distribution package do this:
+
+    cpack
+
+## TODO
+* git hash or tag based versioning depending on source state
+* build tutorial
+* build test
+* with/without language lib/<lang>/
+* enable/disable
+* make cross
+* make dist (create an alias to make package_source)
+* make doc
+* cpack (C++ and make dist only ?)
+  * thrift-compiler
+  * libthrift
+  * tutorial
+  * test
+* merge into /README.md