Renamed some of the operators for parser-combinators to the same as their equivalent functions in fparsec; this fixes some issues with overloading built-in F# operators (||) and (>>) and it'll also make it easier to transition to using fparsec in the future.
Renamed the overloaded (>>) operator to (|>>), the fparsec equivalent.
Added some parentheses around parsing alternatives in 'atomic_preterm' to force the precedece (application order) of the <|> operator and eliminate a number of related errors.
Fixed an errant find-replace.
Fixed another order-of-application error.