Naive impl of "selected" function in expression editor
Refactor: generic expression parse/construct
Set "selected" operator on drop multi-select
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.
update gitignore
fixes #89: don't show question type for choices
fix #87: can't delete extra itext content
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
Merge branch 'develop' into 104232-selected-function-for-staging

Conflicts:
	src/js/ui.js
Merge branch 'develop' into 104232-selected-function-for-staging