3.0.0 Major release

Installation instructions:
https://intelmq.readthedocs.io/en/maintenance/user/intelmq-api.html

• The API endpoint /api/config no longer provides the BOTS file, as it was removed from IntelMQ. The new endpoint /api/bots provides the same information.
• Adapt the configuration file handling to IntelMQ 3.0 (PR#30 by Birger Schacht).
  In IntelMQ 3 the defaults.conf and the pipeline.conf were dropped,
  therefore access to those files via the API is not useful anymore.
  At the same time, the runtime.conf now includes pipeline configuration
  and is stored as a YAML file. Given those changes, the whole
  configuration file handling had to be rewritten: There are now 3 API
  endpoints:
  • /api/runtime to read (get) and write (post) the runtime configuration
  • /api/positions to read (get) and write (post) the positions configuration
  • /api/harmonization to read (get) the harmonization information
    Everything is still done using JSON objects, the conversion to YAML is
    done internally.
    The removal of the save_file method also includes the removal of some
    sanity checks that ran before the file was saved. Some of those should
    probably be part of intelmq itself (i.e. checking for allowed characters
    in bot names).
• fix json output and add error handling (PR#31 by Birger Schacht, fixes #14):
  Hug can not simply return a string that contains json. Therefore the
  content of the files first has to converted to a JSON object.
  This commit also implements simple error handling in case the files do
  not exists or can not be created.
• The version API-endpoint now correctly reports the version of IntelMQ API
  as intelmq-api, not as intelmq-manager (by Sebastian Wagner).