I use brackets .. it uses a folder system rather than a project system so I can just link a set of folders in rather than independently.
http://brackets.io/
I used to use Sublime but got frustrated when jumping between projects. Although, it looks like they do have a folder system that I wasn't aware of.
https://www.sublimetext.com/
I honestly can't remember if it has wowapi on them as I never really worried about it as wowpedia and the wow framexl builds are usually enough.