Merge pull request #188 from mwhite/temp-fix

fix double escaping
Naive impl of "selected" function in expression editor
Refactor: generic expression parse/construct
Set "selected" operator on drop multi-select
fix help icon in firefox
Merge pull request #190 from dimagi/fix-help

fix help icon in firefox
Fail to advanced editor on wrong number of args

This could happen if the user typed an expression like `selected(/data/things, 'thing1', 'thing2')` (which incidentally may not be a valid function call). Previously the third argument would have been silently discarded.
Do not use "selected" function on single-select

The Select mug extends the MSelect, and it inherited its defaultOperator. This fix overrides that default.
Merge pull request #192 from mwhite/temp-fix

fix issues
help icons work on firefox
modify .less to be consistent with new placement of help icon
update artifacts
Merge branch 'master' into develop-nick

Conflicts:
	src/templates/main.html
	style/question-props.css
Merge pull request #193 from dimagi/develop-nick

Develop nick
Ignore develop branch artifacts
Display warning on drop circular reference

...in Display Condition or Calculate Condition.
Refactor/more descriptive warning message
Check mug absolute path as well as "."
Merge pull request #195 from dimagi/85054-warn-on-circ-ref

Display warning on drop circular reference in Display Condition or Calculate Condition
Roll back absolute path check

- It was broken (should have used that.form...)
- There's no way to drag/drop an absolute path anyway.