Update 1,000 Genomes dataset.

Fixes https://github.com/googlegenomics/spark-examples/issues/39
Added a retry for the local credentials store.

An IOException can occur when multiple workers on the same machine try to create the directory to hold the stored credentials.

(Previously this directory was created in advance of running the job when credentials were manually propagated to all workers.)
Updated Google Compute Engine instructions.

Added a link to Click-to-deploy for Hadoop/Spark on GCE from @mbookman

Also simplied gcutil instructions since this job can be invoked by any user.
Merge pull request #42 from deflaux/master

Updates per recent data and runtime environment changes.
Bug fix for NPE when calls do not have additional fields.

Such as in the 1,000 Genomes Phase 3 variants.
Bug fix for another NPE.
Update SearchVariantsExamples to Platinum Genomes.

Per #38
Merge pull request #43 from deflaux/master

Updated all sample datasets to Google Genomics Public Data
Merge branch 'master' into read_benchmarks
Send credentials to the workers to use the refreshToken.

The credentials are serialized as String and sent to the workers where they are reused
when requesting the refreshToken.
Merge branch 'master' into read_benchmarks

Conflicts:
	src/main/scala/com/google/cloud/genomics/spark/examples/rdd/VariantsRDD.scala
Filter empty partitions to prevent dangling listeners.
Added a fixed bases per reference splitter.
Filtered more empty partitions from the multi-threaded version.