split DEPENDENCIES into modules

[florisdenhengst]

The current DEPENDENCIES file lists the dependencies used across all modules.
Since each module is only instantiated once, the scope of this dependency list is too wide.

We could go for either:

• single global dependencies with system-level dependencies and module-specific dependencies files in each module subdirectory. Optionally, we could add a command to create a combined dependencies overview based on the system configuration in core-modules.yaml.
• have a single global dependenices with all dependencies with sections indicating which module-specific dependencies are for which module.

This issue is related to #47