Fix prereq

[ninest]

A list of or groups and and groups isn't enough for preqs. For example, CS 3000:

Actual:

(CS 2510 or DS 2500) and CS 1800 or EECE 2160

Output:

CS 2510 or (DS 2500 and CS 1800) or EECE 2160

[
  [ { subject: "CS", number: "2510" } ],
  [ { subject: "DS", number: "2500" }, { subject: "CS", number: "1800" } ],
  [ { subject: "EECE", number: "2160" } ]
]

[ninest]

Some courses have prereqs (ex, Graduate Admission) which aren't courses

[ninest]

Switching to a structure that looks like

[
  "(",
  "(",
  { subject: "CS", number: "2510" },
  "Or",
  { subject: "DS", number: "2500" },
  ")",
  "And",
  { subject: "CS", number: "1800" },
  ")",
  "Or",
  { subject: "EECE", number: "2160" }
]

which translates to

( ( CS 2510 or DS 2500 ) and CS 1800 ) or EECE 2160

which is more accurate.

Types:

type PrerequisiteItem = "Or" | "And" | "(" | ")" | Requisite | string;

string is included because some courses have prereqs which aren't courses