Add command line arguments

[erichte-ibm]

The program should be able to receive some arguments on the command line to alter its behavior. While we will likely add many more in the future, at least a base system for handling these should be implemented that can be extended later.

At minimum we should support the following:

• [x] -v: verbosity levels, perhaps even printing out the commands being run
• [x] -o: output file, to write the final output to a specific file rather than to stdout
• [x] --allow-failures: do not halt if a collector function fails to obtain data

[erichte-ibm]

mostly implemented in #18 , new command line option requests should be opened as a new issue