Properly handle imported type urls

[ghost]

After thinking about https://cwl.discourse.group/t/proper-syntax-for-type-paths/75

If we have a type definition

- $import: ../tools/Trimmomatic/trimmomatic-end_mode.yaml

should the type usage be

    type: ../tools/Trimmomatic/trimmomatic-end_mode.yaml#end_mode

and If the type definition is

- $import: ./trimmomatic-end_mode.yaml

both

    type: trimmomatic-end_mode.yaml#end_mode

and

    type: ./trimmomatic-end_mode.yaml#end_mode

are valid.

i.e the string following type should be a valid URL that resolves to one of the URL's indicated in an $import statement earlier on in the types field.