[ADAM-416] Removing 'ADAM' prefix

Includes renames for:
* ADAMFeaturesContext class/object.
* ADAMNucleotideContigFragmentContext/RDDFunctions
* ADAMPileupContext/RDDFunctions and ADAMRODRDDFunctions
* AlignmentRecordContext, AlignmentRecordRDDFunctions
* Variation/GenotypeContext

ADAMContext, ADAMRDDFunctions, ADAMVCFInput/OutputFormats, ADAMMetric*,
and ADAMPredicate were all intentionally left unchanged.

Some method names were also changed, to remove the 'adam' prefix as a
particle within the name.
Merge pull request #418 from tdanford/remove-adam-prefix

[ADAM-416] Removing 'ADAM' prefix