Employ JSON Literals instead of tricky json serialized string

[chigix]

It seems that JSON Literals specification drafted for JSON-LD v1.1 has been implemented in Json-ld javascript library:

digitalbazaar/jsonld.js#325

The usage of json serialization as a string should be removed like the following case:

rengular/src/app/shared/simple-quest-script.db.ts

Line 155 in 54e879d

labels: JSON.stringify(TRANSLATION.simpleEntry),