Planar surface about cadquery

[adam-urbanczyk]

I'll plug the free function API here (you'll have to be on master):

from cadquery.occ_impl.shapes import *

# start with a box
b = box(1,1,1)

# split int top face and others
f_top = b.faces('>Z')
f_rest = b.faces('not >Z')

# create the new top face
f_new = f_top + plane(0.5,0.5).moved(f_top.Center())

# assemble into a solid
res = solid(f_rest,f_new)

show_object(res)