Rework client facing information

[sauterl]

Currently, the client bindings primarily provide the means to authenticate participants and to submit both, answers to tasks as well as logs.

There are very basic REST endpoints to get the current evaluation and active task, however we should rework this, including the following (new) features:

• Also send if a task has been selected by the evaluation administrator (and not yet running) - referring to the active task endpoint i.e. change the current task endpoint to a current selected task endpoint
• Expose the submission id upon submitting and add an endpoint which informs about the state of a submission (possibly with rate filtering, such to limit the number of requests for clients) see Rework client facing submission information #477