Add count flag to Parse.Query.find

[BufferUnderflower]

REST api supports adding &count=true.
Using JS SDK one needs to run a separate query.count() to get this number

Would be nice to have some optional flag like query.withCount(true/false) to avoid
making separate async calls

[davimacedo]

I like the idea. We'd need two changes

• In Parse Server side, to receive the additional option and return both results in the same request;
• In JS side, to include the new option in Parse.Query.

@BufferUnderflower is this something that you would be willed to tackle?

[BufferUnderflower]

@davimacedo I've read through js sdk, and stumbled upon in what form should the count be sent back to client. Since query returns the array of Parse.Objects - it's not a good idea to break current api and wrap count and objects array in another object. The only option i see so far is response header like it's done for example in wordpress api

[davimacedo]

The API currently returns in the following format:

{
    "results": [ ... ]
}

We could add a count field and return in the body instead of the header.

{
    "results": [ ... ],
    "count": 30
}