[Task] Support loading all defined concepts of a namespace

[waltersve]

Is your task related to a problem? Please describe.
Currently the loader allows only to load and single aspect. Better would be to allow to load all defined concepts of a namespace e.g. multiple aspect definitions or definitions which are not directly used within the namespace (intended to be used as a reusable definitions).

Describe the solution you'd like
Load all defined concepts and return ist as a map where the key represents the namespace and the values is an array including all definition as object. This would also allow to load multiple .ttl-files with different namespace.

[michelu89]

Is now available on version 2.3.0.