added /MongoNativeCellExtractor
fxed partitions
added mongowriter and improved mongoNativeCellExtractor
aded mongoNativeEntityExtractor and tests
added getPreferredLocations
examples
fixed example
improved partitions
added example using SparkSQL with mongodb
Merge branch 'feature/mongodbNativeSpark' into develop

Conflicts:
	deep-core/src/test/java/com/stratio/deep/core/extractor/ExtractorTest.java
	deep-mongodb/src/main/java/com/stratio/deep/mongodb/config/MongoDeepJobConfig.java