Fix initialization of IsCallee and HasMethodCall constraints

They were not getting a proper origin, causing them to be accidentally
purged at the wrong time.
[browser defs] Fix description of ononline

Closes #418
Make documentation queries also return a type

Issue #409
[emacs mode] Don't suppress errors in highlight-refs

The user will want to know what went wrong.
Make 'completion' hooks completely replace the completion algo

The hook for adding variable completions has been renamed to
variableCompletion.

Issue #412