Trailing comma should result in an error during JSON parsing

Trailing comma should result in an error during JSON parsing

1. QJsonParseError::MissingObject defined
2. QJsonDocument::fromJson() will result in defined error after parsing
of something like "{ 'key':1 , }" or "[ {'key':1}, ]"

Change-Id: I8e6234a03b8aca4e5ad6180f273f91066b86d7a1
Reviewed-by: Lars Knoll <lars.knoll@nokia.com>