Rename the setters in the Window API functions with a !

[NHDaly]

We should rename the Window API functions to be more julian. Either adding a ! at the end of setters, or more explicitly set__ and get__ or is__?

That is, for these ones:
https://github.com/JunoLab/Blink.jl/blob/d984c4d99586c451395cba55eadf8b47d9cac091/src/AtomShell/window.jl#L87-L136

There's a setter and a getter for a bunch of them (position, size, etc).

Can I rename those to position!(w, x, y) and position(w)?

(I came across this as part of #160 😄)

[NHDaly]

Cross Referencing related discussion here: #212 (comment)

[NHDaly]

Another API renaming x-ref: #122 (comment)

load! should be renamed import!.