Clear values on CollectionInputFilter before adding new data

[atodd]

This is related to issue #6304. Instead of calling the clear methods only when there is no value, calling clear on every iteration will prevent data collisions from happening.

[adamlundrigan]

The Travis-CI failures are not related to the code supplied (code coverage generation error).

This code will need tests before it can be merged.

At first glance I'm not certain if this completely fixes the original issue...I will test it out on the codebase where I originally encountered the issue to check. The crux of the issue there is that the structure of the input filter and all it's children is carried over, not the values. I'm away for the weekend but will whip up a test case that illustrates the issue more clearly early next week.

[atodd]

Added a unit test to verify that data from a collection will not be added to a sibling collection in a nested set.

[atodd]

@adamlundrigan have you had a chance to review these changes any further?

[Ocramius]

@atodd merged, thanks!