Large Hadoop stuff refactoring.

* No more context class loader stuff, as it does not work, because Hadoop's Configuration uses its own class loader to find its resources, not the context class loader
* No more trying to load configuration manually, too prone to error

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* Hadoop Jars are now only loaded in the system classloader if DCTC_AUTO_LOAD_HADOOP=tru
* Hadoop configuration is found, either by guessing it from hadoop classpath or from HADOOP_HOME, and is also added to the classloader

* Fix the jars list for Cloudera