Added default_import decorator. [1303]

Having to explicitly import things with console_init.py is tedious;
this decorator allows us to do something like:

    # within file test.py
    @default_import
    def contrivedExampleOne():
        pass

    def internalExample():
        pass

    @default_import
    def contrivedExampleTwo():
        pass

    # within console_init.py
    from test import *

    contrivedExampleOne()
    contrivedExampleTwo()
    internalExample() # error!

I realize that wildcard imports should be discouraged. But…

1. They'd only be happening in one spot. (console_init.py)
2. The end result _shouldn't_ be any different than how things work now.
3. Adding or renaming a function won't require updating console_init.py!