refactor: use a default contentType of application/json in Forms#1176

JKRhb wants to merge 3 commits intoeclipse-thingweb:mastereclipse-thingweb/node-wot:masterfrom

JKRhb:form-default-content-typeJKRhb/thingweb.node-wot:form-default-content-typeCopy head branch name to clipboard