Support Multiple Projects Concurrently

[schwzr]

This is a meta-issue for the implementation of several concurrent projects.

The following steps are necessary:

• project-specific configuration (Support Multiple Projects Concurrently: Project-specific Configuration #141 )
• transfer of a project identifier (Support of dynamic data store selection #134)
• different data sources and sinks depending on the project (Support of dynamic data store selection #134 )
• validation depending on the project (# TBD)
• different pseudonymization configurations depending on the project (# TBD)