Updated Pre-Reqs Functions

Ranamed and updated both preReqs function. We now have getPreReqs(), which will build an array with the ID and Level of all pre-requisites for a skill. We also have testPreReqs() which will return an array based on a skill ID and character ID, indicating if pre-reqs are met or what the failing skill is if they're not. This updates #12 and the code required for it.