refs #2852
- improvement: ensure custom storage adapter has required functions
- serve, save and exists are from now on required functions for a custom storage adapter
- add delete as required storage function
addresses #2852
- Moves storage modules to use prototypes and to create prototypes
that inherit from the base storage ctor.
- Makes storage/base conform to an all Promise interface.
issue #635
- upload controller shouldn't assume fs
- filesystem module proxies all the fs work
- proxies and exposes middleware for serving images
- creating a date based path and unique filename is a base object util
- unit tests updated
