Replace XmlInputFormat with custom DBpediaWikiPageInputFormat.

Necessary changes in DistConfig and DistConfigLoader are also made.
Avoid counting of loaded RDD - lazy evaluation better for performance.
Move InputFormat into input package.
Get thread-local Kryo instance instance of creating one; change var name
Cleaner API with separate overloaded methods.
Fix small String/Byte-array mistake
Close Output instead of just flush - safer.
Add Test for WikiPageWritable
Add Writable implementation for Quads along with unit test.
Merge branch 'hadoop-inputformat' of github.com:dbpedia/distributed-extraction-framework into hadoop-inputformat

Conflicts:
	distributed/src/main/scala/org/dbpedia/extraction/spark/io/input/DBpediaWikiPageInputFormat.scala