Add option for distcp with STORAGE_MIGRATION

[dstreev]

STORAGE_MIGRATION current handles the movement of data through SQL using Hive and the compute layer to run the jobs. There are benefits to this in the sense it provides an opportunity to consolidate and rewrite the data. But sometimes it might just be more efficient to use distcp to move the data and simply change the table's LOCATION information.

This won't work for ACID tables, but could be used for EXTERNAL tables. Changing locations will also mean that we'll need to modify all the partition location information as well.