Merge pull request #92 from jitlogic/dev1

Prepare 0.9.6 release.
Start new iteration.
Factor out SymbolRegistry interface. Move construction of SymbolRegistry/MetricsRegistry to AgentInstance factory object.
Factor out SymbolRegistry/MetricsRegistry interfaces. Move construction of SymbolRegistry/MetricsRegistry objects to AgentInstance factory object.
File-backed persistent symbol registry implementation.
REFACTOR: move metric/trace store related objects to dedicated package.
Metrics file registry.
Refactor symbol/metrics registry into more compact form (merge File*Registry functionality into Simple*Registry).
Get rid of separate File*Registry classes.
Refactor TraceDataHandler / PerfDataHandler into interface.
Filtering in SimplePerfDataFormat.
Traces storage (partial) impl.
Add DS query functionality to agent.