Dcoraid

- enh: introduce APIOutdatedError (server response)
- enh: inform the user to upgrade DCOR-Aid, if the server does not
support the current version
- fix: handle spaces in uploaded resources names (51)
- ref: combine response handling for API GET and POST requests

- fix: properly handle "user_list" for anonymous users
- ref: reorganized APIErros

- fix: APIConflictError "input field id was not expected"
when loading tasks and attempting to create a new dataset

- enh: include datasets share with the user in the "My Data" tab
- fix: catch OSError when trying to load a task that is on an
unmounted network share (48)
- fix: tell users when persistent tasks cannot be loaded because
the paths to the resources are invalid (48)
- ref: extended APIInterrogator by `registry_id` and `__contains__`

- fix: missed a case for task dataset IDs that don't exist but
have been stored in the persistent task dictionary

- feat: allow to add datasets to a collection (11)
- fix: allow empty lines in PersistentTaskDatasetIDDict files
- fix: properly handle task dataset IDs that don't exist (19)