Create system for membership classification

[aviupadhyayula]

As per OSA: clubs should choose between membership classifications. These are currently included under tags, but should be a separate section. Clubs should only be able to select one option.

OSA-defined classifications: Graduate (G), for all graduate & professional; Graduate Open (GO) for primarily graduate & professional, but open to undergraduates; Undergraduate (UG) for all undergraduates; Undergraduate Open (UGO) for primarily undergraduates, but open to graduate & professional.