Override __eq__ in spi classes

[keviny2]

No description provided.

[keviny2]

@jkanche do you think it's appropriate to override __eq__ for SpatialImage?

i had to override __hash__ since lru_cache requires the class to be hashable. but this is problematic because the subclasses are mutable (in place operations).

[jkanche]

That should be ok. This is probably the only place we use lru cache i believe.