Need more than one DIN_LOC_ROOT for Olivia

[gold2718]

Currently, the CIME system allows a single file path location for inputdata, stored in the DIN_LOC_ROOT variable.

On Olivia, it would be much more efficient if DIN_LOC_ROOT could be a searchable list, much like a Linux PATH variable.

A typical use might be something like:

<DIN_LOC_ROOT>local_user_workspace:common_cdl_workspace:/cluster/work/projects/nn9560k/inputdata/</DIN_LOC_ROOT>

Note, we may also want to implement this change for DIN_LOC_ROOT_CLMFORC.

[gold2718]

@matsbn, @mvdebolskiy, @mvertens

[matsbn]

I think this would be quite useful. It allows users to have their own "sandbox" of inputdata for testing/development. If we end up with a write protected common inputdata location on Olivia, this is a place users can store their own input files. To avoid users having useful data for others tucked away in a local user space, there should be a good workflow for ingesting such data into the NS16001B inputdata location on NIRD (and possibly config files for CDL access).