Single-point graphql constructor

[Totktonada]

We should allow to omit explicit data accessor creation and provide graphql constructor receives all needed metainfo and data accessor name. It may look like that:

local gql_wrapper = graphql.new('space', {
    schemas = schemas,
    collections = collections,
    service_fields = service_fields,
    indexes = indexes,
}, {
   ...funcs if needed...
})

Reason: most of users just want to use one of on-board data accessors.

[SudoBobo]

What is the purpose of funcs here?

local gql_wrapper = graphql.new('space', {
    schemas = schemas,
    collections = collections,
    service_fields = service_fields,
    indexes = indexes,
}, {
   ...funcs if needed...
})

To overwrite 'space' or 'shard' functions like unflatten_tuple or get_index?

[Totktonada]

@SudoBobo yep.

[Totktonada]

@SudoBobo Can you please check whether this issue can be closed?

[SudoBobo]

Closed with #95