Add JSON object parsing
Add JSON object parsing

This commit completes the JsonParser class by adding the ability to
parse JSON objects, either alone or inside arrays. JsonParser is now
a JSON parser.

oerdnj/json-glib,brauliobo/json-glib,oerdnj/json-glib,Distrotech/json-glib,oerdnj/json-glib,ebassi/json-glib,brauliobo/json-glib,robtaylor/json-glib-gvariant,ebassi/json-glib,GNOME/json-glib,Distrotech/json-glib,robtaylor/json-glib-gvariant,GNOME/json-glib,brauliobo/json-glib,ebassi/json-glib,frida/json-glib,oerdnj/json-glib,frida/json-glib,Distrotech/json-glib