Global Parquet logging

This should fix [Issue #77](https://github.com/bigdatagenomics/adam/issues/77). Adds an option for the user to specify the level of logging they want (default: severe) and sets Parquet logging level in ADAMMain before the command is run.
The tests are failing with 
```
+ echo 'Converting BAM to ADAM read format'
Converting BAM to ADAM read format
+ java -Xmx1g -jar adam-0.12.1-SNAPSHOT.jar bam2adam -samtools_validation lenient mouse_chrM.bam mouse_chrM.bam.reads
"-samtools_validation" is not a valid option
 -h (-help, --help, -?)                                          : Print help
 -parquet_block_size N                                           : Parquet block size (default = 128mb)
```
The reason that is happening is that InitArgs doesn't know about the full list of options for each command. You'll need to update the Arg4j class to support ignoring unknown options *or* manually parse the parquet log option.