add support for organizeImports command

[ananthakumaran]

this command is only available on Typescript master branch

[josteink]

Woo! Another feature!

Based on what I read here, it seems all this should do is sort the imports. I've tested that, and it seems to work for me.

Besides that, the code changes looks good to me. I especially like the new way of handling compatibility.

I'd preferred it to be split over 2 commits (refactor, add feature), but now that it's already done, I'm not sure it's worth the trouble splitting up.

I'm OK with this getting merged as is. Good job :)

[ananthakumaran]

Thanks, I kind of got lazy and did the refactor in the middle.