create_dt: more prep work for switch to generating all dt files

* Added indexes for PWMs to bone.js
* Enabled create_dt to be synchronous by checking for slot loads
* Separated out function for waiting on dt slot loads
* Added parameters to skip loading and force dtbo generation
Merge branch 'master' of github.com:jadonk/bonescript
Move constants into separate file
Merge branch 'master' of github.com:jadonk/bonescript