ENH: Multidimensional image-sequence

`ImageSequence3D` class derived from `ImageSequence`.
Imports t, z, c indexed .tif files. Output is indexed with t index and can be 2/3/4 dimensional.
Don't use mutable objects as default values unless you _really_ mean to:

```python
def foo(bar=[]):
    bar.append('baz')
    print(bar)

foo()
foo()
foo()
```

It is safer to have the default to be None, then check and use the list or just make this a tuple.