MAINT: add changelog, license and release guide

CHANGELOG.md

+# Changelog
+
+All notable changes to this project will be documented in this file.
+
+The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.1.0/),
+and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
+
+## [0.9.0] - 2022-08-30
+(Henrik tom Wörden)
+
+### Added
+
+* a `Dockerfile` to build the CaosDB docker image and a `docker-compose.yml`
+  that allows to start the CaosDB server.
+
+### Changed
+
+### Deprecated
+
+### Removed
+
+### Fixed
+
+### Security
+

RELEASE_GUIDELINES.md

+# Release Guidelines for the CaosDB Server
+
+This document specifies release guidelines in addition to the general release
+guidelines of the CaosDB Project
+([RELEASE_GUIDELINES.md](https://gitlab.com/caosdb/caosdb/blob/dev/RELEASE_GUIDELINES.md))
+
+## General Prerequisites
+
+* All tests are passing.
+* CHANGELOG.md is up-to-date.
+
+## Steps
+
+1. Create a release branch from the dev branch. This prevents further changes
+   to the code base and a never ending release process. Naming: `release-<VERSION>`
+
+2. Check all general prerequisites.
+
+3. Update the versions in:
+  * `CHANGELOG.md`
+  * ?
+
+5. Merge the release branch into the main branch.
+
+6. Tag the latest commit of the main branch with `v<VERSION>`.
+
+7. Delete the release branch.
+
+8. Merge the main branch back into the dev branch.
+
+9. Update the versions for the next developement round:
+  * `CHANGELOG.md`: Re-add the `[Unreleased]` section.
+  * ?
+
+10. Add a gitlab release in the respective repository:
+    https://gitlab.indiscale.com/caosdb/src/caosdb-server/-/releases
+
+    Add a description, which can be a copy&paste from the CHANGELOG, possibly prepended by:
+    ```md
+# Changelog
+
+[See full changelog](https://gitlab.indiscale.com/caosdb/src/caosdb-docker/-/blob/v0.7.3/CHANGELOG.md)
+    ```