Change guice managed JdbcHelper to static utility

Not really getting much benefit from this being a guice managed
dependency, better to simplify.
Eliminate HttpHandler interface

Rename SimpleHttpServer to HttpServerBase and change it to an abstract
base class in order to eliminate the need for the HttpHandler interface.
Rename TraceRepository to TraceSink

Help clarify that it is a uni-directional storage pipe and not a
traditional store/read "entity repository".  Also, send all completed
traces to the TraceSink and perform threshold filtering in TraceSink.

Also rename MetricRepository to MetricSink.
Move all json services to local.ui package

This eliminates the local.configuration package (keeping the number of
packages down).
Rename a package and a couple of classes

local.metrics -> local.metric for consistency with local.trace
ReadTraceRequest -> TraceRequest for brevity
ReadMetricRequest -> MetricRequest for brevity
MetricPointDao -> MetricDao for brevity and consistency with TraceDao
Remove an unused method
Change TraceSink to an interface

An abstract base class isn't really needed.  Can always create a common
base class, e.g. TraceSinkBase, to support common functionality across
TraceSink implementations.
Use TraceRegistry directly instead of TraceService

TraceService is not needed in StackCollector or in StuckTraceCollector
other than for access to TraceRegistry.
Merge TraceService into PluginServicesImpl

TraceService is now only used by PluginServicesImpl and can be removed
which simplifies the guice dependency injection graph.
Add jquery ui button module
Implement page to view traces
Implement page to view and update settings
Remove unused snapshot repository from pom.xml
Remove unused snapshot repository from pom.xml
Support maven 2.2.x (in addition to 3.0.x)
Support maven 2.2.x (in addition to 3.0.x)
Support sql server
Fix excessive logging when viewing a large trace
Handle trace unexpectedly exceeding a threshold

This can happen if threshold settings are changed mid-trace.  Also
it could happen if the scheduled executor service falls behind.
Display merged stack trees in traces ui