Avoid Quartz lazyloader `from Quartz import *` bug

- Change `from Quartz import *` to the fast `import Quartz`, and update
  all references to Quartz objects to be explicit.
- Add unit test checking import times for pymouse package

pyobjc's lazyloader makes the form `from ... import *` very slow. This
can make importing pymouse extremely slow on OS X due to its use of
from Quartz import *.

See the issue discussion on the pyobjc project:

https://bitbucket.org/ronaldoussoren/pyobjc/issue/2/faster-metadata-support

From that thread on 2013-07-16:

> If you are only using framework wrappers: make sure you do not use "from
> Foundation import ", use "import Foundation" or "from Foundation import
> NSObject" instead. Someone recently noticed that the "from ... import "
> form is currently much slower than it used to be, due to the way the
> PyObjC lazy loader is implemented. I'm working on a fix for that, but
> even with the fix explicit imports will be better because they perform
> less form (because explicit imports don't have to resolve the symbols
> you don't use).

pymouse has this exact problem due to its use of `from Quartz import *`:

    $ time python -m pymouse
    ...
    real	0m16.040s
    user	0m14.322s
    sys	0m0.194s

Changing to just `import Quartz` solves the extremely long hang at
import time problem; after this commit:

    $ time python -m pymouse
    ...
    real	0m0.558s
    user	0m0.390s
    sys	0m0.087s