Support for Cloudera Hadoop

# Cloudera Hadoop Support for Ozone
These changes allow to use and easily switch between different Hadoop versions.

## How to use:
- adjust the hadoop version in the main pom (samples for Hadoop 0.20.203.0 and 2.0.0-cdh4.2.1 are provided)
- adjust all poms that require Hadoop to use the correct jar names (hadoop-core changed to hadoop-common, hadoop-hdfs may need to be added)

## Side effects:
Different Hadoop versions use different jar names and have different dependencies that need to be added to the classpath.
Previously all jar names were explicitly listed in the application startup scripts. While this allows for tailor-made classpaths it is also a major maintenance overhead.
The behavior was changed so the startup scripts now add all jars from the <ozone_root>/lib folder to the classpath.
Jars required by pact-clients have been moved to lib_clients, to avoid unnecessary overhead for worker tasks.
In the end this means far less classpath management overhead while retaining a reasonably clean classpath.