Generalize Reflector geometry

[WestLangley]

Reflectors do not have to be rectangular. Any planar geometry will work.

The change here is trivial, but this PR will break other examples that depend on Reflector.

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Ugh. There is some weird end-of-line character thingy going on that makes this PR seem bigger than it is. :/

[Mugen87]

The same should be true for Refractor and Water, too.

We should keep these objects equal so i think it's better to change and test them together.

[mrdoob]

This is great!

[mrdoob]

The change here is trivial, but this PR will break other examples that depend on Reflector.

I think that's ok in this case. I'll try to release the next version soon.

The same should be true for Refractor and Water, too.

Agreed! Do you want to do it in this PR or leave it for a different PR?

[WestLangley]

@Mugen87 @mrdoob I added additional commits as requested. I did not touch Water.js or Water2.js because I feel they can be considered separately -- unless I am missing something...

[mrdoob]

Looks good! Merging for now.

[mrdoob]

Thanks!