Minor revisions

[ClemensBuechner]

I've implemented several minor changes discussed during the code-walk meetings with @FlorianPommerening and @roeger. They don't change anything about the logic but are concerned with renaming stuff for clarification and other minor things to prettify and clean up the code. Here is a list of the changes:

• Return floating point number when randomly sleeping before submitting jobs to the grid.
• Replace True if x else False with x.
• Ensure files are closed after reading/writing.
• Rename result files on the grid to exit_code and reduce their content to only the exit code without a string that needs to match around it.
• Rename enforce_order to allow_nondeterministic_successor_choice.