Revert "Metrics for prepared stmt usage and eviction"

This reverts commit 19c6cc1982d2146a99ccaf6dccc087fe88d5785f.
Merge branch 'cassandra-2.0' into cassandra-2.1

Conflicts:
	CHANGES.txt
	src/java/org/apache/cassandra/cql3/QueryProcessor.java
Merge branch 'cassandra-2.1' into trunk