rework bones namespace to have broot as root of namespace in Python

[DangerMouseB]

i.e. so the user does something along the lines of:

from broot import *
A >> broot.dm.linalg.np.qr>> solve >> x

or

from broot import *
from broot import dm
A >> dm.linalg.np.qr >> solve x

[DangerMouseB]

done