Possibly replace check and cross marks with simple characters

[okkhoy]

Many students can't get the tick and cross marks to work either in the IDE or in the terminal or both.
They end up spending time on getting that right.
Instead, we could replace those with simple characters Yes and No for the status.
See nus-cs2113-AY2021S1/forum#31 for a context.

[damithc]

Yes, we should do that next time.

[damithc]

Done