move jstreetypes to util
generate jstreetypes from question types

(and make fieldlist able to be a child of a group or repeat)
refactor jstree icon overriding to be more maintainable
remove further question type indirection
remove unused typeName attribute
single point of truth for question type slug
remove unused name property
make question name and icon part of the mugtype definition, and refactor to enable that
add missing jstree types
fix order of includes in tests
Merge branch 'master' of github.com:dimagi/Vellum into cleanup
Merge branch 'master' into cleanup
Merge pull request #95 from dimagi/cleanup

refactoring related to types; also allow field list in groups