Don't include the namespace in the import's name for hy models.

[gilch]

Brandon Rhodes expressed it well at PyCon
https://youtu.be/x-kB2o8sd5c?t=1048

In his example,

import piano
piano.Bench()      # yes!

Is preferable to

import piano
piano.PianoBench()  # no!

We should not bake the namespace into the name itself.

Similarly for the Hy models, we should have

hy.List
hy.Expression
hy.Dict

etc. not

hy.HyList
hy.HyExpression
hy.HyDict

like we have now.

[Kodiologist]

Contrast with #1045.

[refi64]

We could always import hy automatically, which also pollute the global scope a bit less.

[gilch]

We could also leave eval in there but not auto import from hy.core.language import eval like we do now.

Then Hy's eval would be hy.eval, (not hy.hy-eval) and Python's builtin would just be eval.