Sepatrate directories for types

[Zarquan]

This is the ideal structure - if the OpenAPI code generator will let us.

The first file in each directory contains the abstract type with discriminator map. Subsequent files contain the individual types.

schema
   |
   +-- types
         |
         +-- executable
         |      |
         |      +-- executable-types.yaml
         |      |
         |      +-- jupyter-notebook.yaml
         |      |
         |      +-- docker-container.yaml
         |      |
         |      \-- singularity-container.yaml
         |
         +-- resources
               |
               +-- data
               |     |
               |     +-- data-resources.yaml
               |     |
               |     +-- simple-data-resource.yaml
               |     |
               |     +-- S3--data-resource.yaml
               |     |
               |     +-- rucio--data-resource.yaml
               |     |
               |     \-- ivoa--data-resource.yaml
               |               
               +-- storage
               |     |
               |     +-- storage-resources.yaml
               |     |
               |     \-- simple-storage-resource.yaml
               |
               +-- compute
                     |
                     +-- compute-resources.yaml
                     |
                     \-- simple-compute-resource.yaml