Allow share directory prefixing

[adamrlynch]

Feature Idea: Allow share directory prefixing

User Case:

Current functionality drops all created shares at the root of the volume specified in location. This can result in a messy directory when that volume is shared and contains directories used for other things. It would be ideal to be able to place all created shares within a directory on the volume.

Implementation

While this functionality could be replicated by prefixing the path in the PVC this puts ownness on the developer to remember to do that. By allowing the storage class to add a directory prefix this simplifies deployment when developers just want to use an existing storage class rather than creating the PVC themselves.