Add present working course command

[Maia Lalor]

In the Clanvas shell, the default prompt adds functionality parallel to what most shells have with the cd (change directory) command. Clanvas has a cc (change class) command, which then implicitly passes that course to all the command that require a course to be specified (for example, lg (list grades) can be called after a cc call, or one can use the -c option to specify a course explicitly or a course other than the current one).

Add a pwc (present working class) command (analogous to the pwd (present working directory) command) that outputs information about the class that is currently selected with cc.

Now, there is a bit more information about courses than there is about directories, so I imagine the command would be a bit more complex than the pwd command, here is how I imagine some example output:

Command: pwc

EECS455-13682

Command: pwc -l

Name: Applied Graph Theory (100/10395)
Course code: EECS 455
Term: Fall 2018
Course id: 13682

If no course has been selected, something like the following would make sense.

Command: pwc

No course selected. Use cc to select a course.