Allow empty env.config in config yaml file

[rdnfn]

Problem

There can be issues with setting env.config to None/null in a config file or leaving out this setting entirely. This is because some parts of the scheduler assume a non-empty env.config. This issue was originally raised in #82 by @HYDesmondLiu.

Potential Solution

There are multiple ways to achieve this:

1. automatically add env config if empty (requires access to this in code).
2. remove call to config outside env_creator script.

[rdnfn]

On the current dev version, the name attribute is no longer required anywhere in Beobench scheduler or agent code. Thus, this issue will be resolved in the next release.