Start JWST MIRI implementation

[mperrin]

Placeholder issue for initial implementation of JWST MIRI support. Many details TBD.

[mperrin]

@AlexBidot has started this

[mperrin]

See PR #44

[jruffio]

Given the PR, and that there is a separate issue #47 about adding missing docs for MIRI. I am closing this.

[jruffio]

Sorry I messed up, reopening, somehow I thought we had already merged the MIRI branch... Looks like Alexis was still trying to test something else before merging.