no escaping in json keys /sql?mode=raw

[githubmanticore]

/sql?mode=raw can return invalid JSON due to the lack of escaping of keys, e.g. http://localhost:9308/sql?mode=raw&query=select%20concat(%27%22%27,%20%27a%27)

[{ 
"columns":[{"concat('"', 'a')":{"type":"string"}}], 
"data":[ 
{"concat('"', 'a')":"\"a"} 
], 
"total":1, 
"error":"", 
"warning":"" 
}] 

The task is to add escaping. As discussed with Alexey it can cause slower response rendering, but I find it ok since /sql?mode=raw shouldn't be used for things where it's critical to have as fast rendering as possible (select/insert/replace/update/delete).

[sanikolaev]

fixed in 36efc60