Data filter falsey

[github-abcde]

What does this PR do?

This adds a function filter_falsey to salt.utils.data. The function can be used to filter values from a list or dict that evaluate to false (but are not bool(False)). Optionally, a level of recursion can be set to process nested dicts/lists. Also optionally, a list of types to not filter can be passed in ignore_types.

What issues does this PR fix or reference?

None that I know of.

Previous Behavior

The functionality does not exist.

New Behavior

We are now able to filter falsey values from dicts or lists.
This is especially handy when having to process a lot of kwargs that are explicitly specified in the function argument list, which default to None, but need not be passed on if they are None.
For example:

def some_function(foo=None, bar=None, baz=None):
    new_kwargs = {}
    if foo is not None:
        new_kwargs.update('Foo': foo)
    if bar is not None:
        new_kwargs.update('Bar': bar)
    if baz is not None:
        new_kwargs.update('Baz': baz)
    some_other_function(**new_kwargs)

will become

def some_function(foo=None, bar=None, baz=None):
    new_kwargs = salt.utils.data.filter_falsey({
        'Foo': foo,
        'Bar': bar,
        'Baz': baz,
    })
    some_other_function(**new_kwargs)

Which is a typical use-case for most Boto calls.

Tests written?

Yes

Commits signed with GPG?

Yes

[github-abcde]

@twangboy I've implemented the changes you requested. Is there anything else I can do for this PR?

[twangboy]

@github-abcde Looks good. Thanks!