cd and pwd commands

[bmart847]

Complete the cd and pwd commands. Update shell for these commands. Update design
and test plans as needed.

[bmart847]

I put these two in one issue since they'll be very similar. cd command will simply be changing the working directory and pwd command will display it.

[bmart847]

pwd has been working. We'll keep this issue open for cd tho

[bmart847]

pwd is also done after our restructuring. cd still to come

[joeListro]

CD should now be working on CMD--CD branch

[bmart847]

restructure now gives cd full access to shared mem and changes the dir. needs to make sure that dir exists tho, so we may need to merge in changes you made. pull request? have a look at cd when you can

[bmart847]

on branch testing, cd is now checking for existence.