Spark history file processing

Enables the preprocessing, rawloader and processing steps to process Spark history/conf files.

Ensures the "spark" prefix is applied to spark jobs, but backwards compatibility is maintained for hadoop jobs. hRaven till now presumed the prefix to be "job" for all job ids. All the JobIds, JobKeys, Row keys did not contain this prefix , but now we need to add existence of such a prefix to include spark files.

Adds SparkJobDescFactory, JobHistoryFileParserSpark classes

If the processing step is going to be run on a hadoop1 cluster, then jackson-1.8.8 libraries need to occur in the classpath before the jackson-1.5.2 libraries . The jackson 1.5.2 libraries come with hadoop. 
Hence we need set -Dmapreduce.task.classpath.user.precedence=true parameter at the processing step and add $(ls /usr/local/hbase/lib/jackson-core-asl-*.jar),$(ls /usr/local/hbase/lib/jackson-mapper-asl-*.jar) to the libjars at the processing step for hadoop1 clusters.

Yes, I could not change that one since the Interface had that Long as the return type. Also in the getMegaByteMillis in other parsers, there are places where null is being returned (which can be changed to return 0 but that would be several more changes in existing code, which I would rather not do right now) ,hence had to keep this one as Long