Rough implementation of sort tool. Generate lots of smaller sorted (STL sort with...

Rough implementation of sort tool.  Generate lots of smaller sorted (STL sort with 'custom' compare fxn) temp files in one pass, using a specified buffer size.  Uses BamMultiReader paired with BamWriter to re-merge all temp files back into a single output BAM, also in one pass. Some work remains on optimizing parameters (e.g. default buffer size), scalability (single pass generates lots of temp files), & parallelization to make tool more sophisticated & robust.