Move API doc descriptions completely to actinia-api

[mmacata]

Follow up from https://github.com/mundialis/actinia_core/pull/278 In the modules in rest folder, API docs are still defined above the HTTP methods. They should also be moved to actinia-api.

Also move version definition to this repo (e.g. v3). Then importing plugins/libs also need to be adjusted!

[anikaweinmann]

Pull Requests:

• actinia-api: https://github.com/mundialis/actinia-api/pull/4
• actinia_core: https://github.com/mmacata/actinia_core/pull/5
• actinia_statistic_plugin: https://github.com/mundialis/actinia_statistic_plugin/pull/12
• actinia-stac-plugin: https://github.com/mundialis/actinia-stac-plugin/pull/55 (TODO)
• actinia_satellite_plugin: https://github.com/mundialis/actinia_satellite_plugin/pull/10
• actinia-module-plugin: https://github.com/mundialis/actinia-module-plugin/pull/21
• actinia-tiling-plugin:
• actinia-example-plugin: https://github.com/mundialis/actinia-example-plugin/pull/2 (TODO)
• actinia-metadata-plugin: https://github.com/mundialis/actinia-metadata-plugin/pull/7