v0.9.0

• Removed deprecated warnings about the sampling interface (and the old sampling interface).
• New feature: Access interim results from counters without stopping the counter using live counters.
• New feature: Sampling the user stack.
• New feature: Create custom metrics using expressions, e.g., "instructions/cycles".
• New feature: Use metrics when sampling counter values.
• New feature: Control scheduling of events to physical hardware counters.
• New feature: Added time events (e.g., seconds, milliseconds, etc.) as virtual counters.