Unit Test By Window Variant

Split the unit tests up to match the implementation files.
Add unit tests for https://github.com/ReactiveX/RxJava/issues/1546 to OperatorWindowWithSizeTest
Fixes Early Unsubscribe for Non-Overlapping Window

https://github.com/ReactiveX/RxJava/issues/1546
Fixes Early Unsubscribe for Overlapping Window

- https://github.com/ReactiveX/RxJava/issues/1546
- This also fixes the fact that the overlapping window overload was not propagating unsubscribe before. A new unit test caught that.
Merge pull request #1829 from benjchristensen/1546-window

Fix Window by Count Unsubscribe Behavior