Cleaning up the warehouses, making most methods const, avoiding vector copies
closes #3358, #3368
Merge pull request #3377 from permcody/warehouse_cleanup

Cleaning up the warehouses
Merge commit '24f6b712e474e73849d278296c661c09f7359776'
Removed vector copy
(refs #3378)
Merge pull request #3386 from aeslaughter/output_warehouse-3378

Removed a vector copy from OutputWarehouse
Merge commit '4bda14fb545aa269c6634ff348f14821b0d181ef'