Add missing classmethods PVector

[albertjan]

for example: PVector.add()

[eah13]

Seems like our PVector also doesn't accept floats in __init__ like processing.py does: https://trinket.io/python/b28182978b

[albertjan]

http://py.processing.org/reference/PVector.html according to the docs they have to be ints

[albertjan]

https://trinket.io/python/b0e5b12e7f

[albertjan]

Thats an error in the documentation, and we're probably also missing some functions on PVector by the looks of it.

[
'__add__', '__class__', '__copy__', '__deepcopy__', '__delattr__', '__dict__', '__div__', '__doc__',
'__ensure_finalizer__', '__eq__', '__format__', '__ge__', '__getattribute__', '__gt__', '__hash__', 
'__iadd__', '__idiv__', '__imul__', '__initProxy__', '__init__', '__instance_add__', '__instance_cross__', 
'__instance_dist__', '__instance_div__', '__instance_dot__', '__instance_lerp__', '__instance_mult__', 
'__instance_sub__', '__isub__', '__le__', '__lt__', '__module__', '__mul__', '__ne__', '__new__', '__reduce__', 
'__reduce_ex__', '__repr__', '__rmul__', '__setattr__', '__str__', '__sub__', '__subclasshook__', 
'__supernames__', '__unicode__', '__weakref__', '_getPyInstance', '_getPySystemState', 
'_setPyInstance', '_setPySystemState', 'add', 'angleBetween', 'array', 'class', 'classDictInit', 'clone', 
'copy', 'cross', 'dist', 'div', 'dot', 'equals', 'finalize', 'fromAngle', 'get', 'getClass', 'hashCode', 
'heading', 'heading2D', 'lerp', 'limit', 'mag', 'magSq', 'mult', 'normalize', 'notify', 'notifyAll', 
'random2D', 'random3D', 'rotate', 'set', 'setMag', 'sub', 'super__add', 'super__copy', 'super__cross', 
'super__dist', 'super__div', 'super__dot', 'super__get', 'super__lerp', 'super__mult', 'super__sub', 
'toString', 'wait', 'x', 'y', 'z']

vs:

[
'__eq__', '__ge__', '__getattr__', '__gt__', '__hash__', '__init__', '__le__', '__lt__', '__module__', '__ne__', 
'__new__', '__repr__', '__setattr__', '__str__', 'add', 'angleBetween', 'array', 'cross', 'dist', 'div', 'dot', 
'get', 'limit', 'mag', 'mult', 'normalize', 'set', 'sub']