Sub entities in sandbox work directory

[dddjef]

When a resource has nested entities this should be reflected by subfolder in work sandbox.
(ie : ep104.sh15-animation will have a path work/ep104/sh15-animation/)

[dddjef]

this function will then need an update : uri_standards.path_to_uri
This update will require to determine what's the resource path in an arbitrary path, hence it could require an identified pulse data file inside it

[dddjef]

#83 would adress the issue about determining the resource root directory