Improved pool metrics.

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# Cambios para hacer commit:
#	modificado: splout-hadoop/src/main/java/com/splout/db/hadoop/SchemaSampler.java
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# Archivos sin seguimiento:
#	CHANGES.txt~
#	README.md~
#	out-com.splout.db.hadoop.TestTablespaceGenerator/
#	out-com.splout.db.hadoop.TestTablespaceGeneratorJavaScript/
#	splout-hadoop/.in-com.splout.db.hadoop.TestTablespaceGeneratorJavaScript.crc
#	splout-hadoop/.input-com.splout.db.hadoop.TestTupleSampler_1.crc
#	splout-hadoop/.input-com.splout.db.hadoop.TestTupleSampler_2.crc
#	splout-hadoop/.input-com.splout.db.hadoop.TestTupleSampler_3.crc
#	splout-hadoop/.input-com.splout.db.hadoop.TestTupleSampler_r.crc
#	splout-hadoop/.output-com.splout.db.hadoop.TestTupleSampler_1.crc
#	splout-hadoop/.output-com.splout.db.hadoop.TestTupleSampler_2.crc
#	splout-hadoop/.output-com.splout.db.hadoop.TestTupleSampler_3.crc
#	splout-hadoop/.output-com.splout.db.hadoop.TestTupleSampler_r.crc
#	splout-hadoop/database-files/
#	splout-hadoop/ddate.json
#	splout-hadoop/derby.log
#	splout-hadoop/idadvertiser.json
#	splout-hadoop/idpublisher.json
#	splout-hadoop/metastore_db/
#	splout-hadoop/pangool-instances/
#	splout-hadoop/src/main/java/com/splout/db/benchmark/TablespaceAnalyserCMD.java
#	splout-server/dnode-staging-0/
#	splout-server/dnode-staging-1/
#	splout-server/dnode-staging-2/
#	splout-server/hz-data/
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