Added c.t.DecoratorTap class to simplify wrapping a given c.t.Tap instance with additional meta-data. Updated c.f.p.FlowPlanner to allow both intermediate temporary c.t.Tap or any c.p.Checkpoint tap to be decorated by a configured c.t.DecoratorTap class via new c.f.FlowConnectorProps properties.
Added c.t.h.DistCacheTap a decorator for a c.t.h.Hfs instance that uses o.a.h.f.DistributedCache to read files transparently from local disk. This is useful for c.p.HashJoins.
Allow registration of tracing barriers. This commit adds a mechanism
for registering regexes that serve as barriers for tracing. As
a concrete example, Scalding can add a barrier that says anything
in the com.twitter.scalding package should be seen as an entry point so
that the caller of Scalding is logged in the trace instead of the
Scalding code such as RichPipe.