DRILL-996 - Allow other versions of Hadoop to be specified on command-line

Example usage:
- mvn install -DskipTests -Dapache.hadoop.version=1.1.0
- mvn install -DskipTests -Drat.numUnapprovedLicenses=1000 -Pmapr -Dmapr.hadoop.version=1.0.3-mapr-3.1.1 -Dmapr.hbase.version=0.94.17-mapr-1405-m7-3.1.1
- mvn install -DskipTests -Pcdh -Dcdh.hadoop.version=2.3.0-cdh5.0.2
- mvn install -DskipTests -Phdp -Dhdp.hadoop.version=2.4.0.2.1.2.0-402

However, this violates the Maven principle of the POM describing the JAR's dependencies. Scripting to change the POM itself was considered inappropriate at this time.