Add integration test demonstrating that filters of queries fire events across browsers and refs
Modify last test so it fails for filter fns involving + (plus chars)
Add '+' as special character to handle for '_$queries.*' paths

Fixes issue where refs pointing to filter paths of filters using functions with
a "+" ended up not emitting up the ref chain.
Handle onRmDoc in edge case where pointerIds is undefined
Allow null query comparands
Merge pull request #1 from SLaks/patch-3

Merge bugfix & latest changes