the env object can be used to alter and edit the content of environment
variables. Additionally, the class efl.core.env can be used to to setup
a not applied set of environment variables, which then can be applied
later (in the future) to set it directly to a spawned process for
example, or as a general key/data storage. A efl.core.env object can
also be forked off, which makes it easy to customize predefined objects.