Add utility methods for adam-shell

[heuermh]

E.g.

scala> import org.bdgenomics.adam.rdd.ADAMContext._
import org.bdgenomics.adam.rdd.ADAMContext._

scala> import org.bdgenomics.adam.util.ADAMShell._
import org.bdgenomics.adam.util.ADAMShell._

scala> val variants = sc.loadVariants("Mills_and_1000G_gold_standard.indels.variants.adam")
variants: org.bdgenomics.adam.rdd.variant.VariantRDD = ParquetUnboundVariantRDD with 3366 reference sequences

scala> printVariantFilters(variants)
Filter Header Lines
FILTER=<ID=PASS,Description="Truth sensitivity tranche level at VQS Lod < -381.3592">

Variant Filters
+-------------+--------+--------+-------+--------+-----------------+----------------+----------------+
| Contig Name | Start  |  End   |  Ref  |  Alt   | Filters Applied | Filters Passed | Filters Failed |
+-------------+--------+--------+-------+--------+-----------------+----------------+----------------+
|        chr1 |  55248 |  55249 | C     | CTATGG |            true |           true |             [] |
|        chr1 |  87113 |  87115 | CT    | C      |            true |           true |             [] |
|        chr1 | 263834 | 263837 | CCT   | C      |            true |           true |             [] |
|        chr1 | 756186 | 756191 | CACAG | C      |            true |           true |             [] |
|        chr1 | 779928 | 779930 | AG    | A      |            true |           true |             [] |
|        chr1 | 786693 | 786694 | A     | ATT    |            true |           true |             [] |
|        chr1 | 796753 | 796754 | T     | TA     |            true |           true |             [] |
|        chr1 | 816926 | 816928 | AT    | A      |            true |           true |             [] |
|        chr1 | 822795 | 822798 | CCT   | C      |            true |           true |             [] |
|        chr1 | 824063 | 824068 | ATATT | A      |            true |           true |             [] |
+-------------+--------+--------+-------+--------+-----------------+----------------+----------------+

[AmplabJenkins]

Test PASSed.
Refer to this link for build results (access rights to CI server needed):
https://amplab.cs.berkeley.edu/jenkins//job/ADAM-prb/2732/
Test PASSed.

[fnothaft]

Nice! This is a great idea! Did you want to add to this, or would you be OK with me merging this into 0.24.0?

[heuermh]

Did you want to add to this, or would you be OK with me merging this into 0.24.0?

There is probably more to add, but if you think the pattern is right, then merging into 0.24.0 is ok with me. I'll squash into one commit.

[AmplabJenkins]

Test PASSed.
Refer to this link for build results (access rights to CI server needed):
https://amplab.cs.berkeley.edu/jenkins//job/ADAM-prb/2733/
Test PASSed.

[fnothaft]

Merged! Thanks @heuermh!