Implement Display for points

[jotabulacios]

Printing points currently produces confusing output:

point: ShortWeierstrassProjectivePoint(ProjectivePoint { value: 
[FieldElement { value: UnsignedInteger { limbs: [3280788209096359030, 3523508710880940061, 10293639770089035364, 17681286407857937546] } }, 
FieldElement { value: UnsignedInteger { limbs: [3123146678334417656, 15201872240025911839, 7991108154579521779, 6258186992099579766] } }, 
FieldElement { value: UnsignedInteger { limbs: [1011752739694698287, 7381016538464732716, 754611498739239741, 15230403791020821917] } }
] })