Move PSCi Temp Module from Main to $PSCI 

This fixes #530 and (surprisingly) #531. 

I also added a case in `getCommand` to re-print the prompt when a user enters no command into PSCi, instead of trying to parse a multi-line expression like before. As far as I can tell, this changes nothing in terms of functionality but allows users to press enter to put space between commands instead of having to press `ctrl+d` after a couple of presses of Enter. If this is undesired or messes anything up I'll take it out, but it seemed buggy to me before.