Callbacks enhancement - #851

Query:
 type: object
 config:
 fields:
 user:
 type: User
 resolve: '@=query("query")'
User:
 type: object
 config:
 fields:
 name:
 type: String
 description: "the user name"
 friends:
 type: friendConnection
 argsBuilder: "Relay::Connection"
 resolve: '@=query("friends", value, args)'
 friendsForward:
 type: userConnection
 argsBuilder: "Relay::ForwardConnection"
 resolve: '@=resolver("friends", [value, args])'
 friendsBackward:
 type: userConnection
 argsBuilder: "Relay::BackwardConnection"
 resolve: '@=resolver("friends", [value, args])'
friendConnection:
 type: relay-connection
 config:
 nodeType: User
 resolveNode: '@=query("node", value)'
 edgeFields:
 friendshipTime:
 type: String
 resolve: "Yesterday"
 connectionFields:
 totalCount:
 type: Int
 resolve: '@=query("connection")'
userConnection:
 type: relay-connection
 config:
 nodeType: User
 resolveNode: '@=query("node", value)'

Query:
 type: object
 config:
 fields:
 user:
 type: User
 resolver: 'Overblog\GraphQLBundle\Tests\Functional\App\Resolver\ConnectionResolver::resolveQuery'
User:
 type: object
 config:
 fields:
 name:
 type: String
 description: "the user name"
 friends:
 type: friendConnection
 argsBuilder: "Relay::Connection"
 resolver:
 method: 'overblog_graphql.test.resolver.node::friendsResolver'
 friendsForward:
 type: userConnection
 argsBuilder: "Relay::ForwardConnection"
 resolver:
 id: 'overblog_graphql.test.resolver.node'
 method: 'friendsResolver'
 friendsBackward:
 type: userConnection
 argsBuilder: "Relay::BackwardConnection"
 resolver: 'overblog_graphql.test.resolver.node::friendsResolver'
friendConnection:
 type: relay-connection
 config:
 nodeType: User
 resolveNode: '@=query("node", value)'
 edgeFields:
 friendshipTime:
 type: String
 resolver: 
 expression: "'Yesterday'"
 connectionFields:
 totalCount:
 type: Int
 resolver: '@=query("connection")'