autocomplete json, add information about variadics

Summary: There are two types of variadics

  function t2(int $a, string ...$a);
  function t1(int $a, ...);

Respective outputs are

            "params": [
                {
                    "name": "$a",
                    "type": "int",
                    "variadic": false
                },
                {
                    "name": "$args",
                    "type": "string",
                    "variadic": true
                }
            ],

and

            "params": [
                {
                    "name": "$a",
                    "type": "int",
                    "variadic": false
                },
                {
                    "name": "",
                    "type": "_",
                    "variadic": true
                }
            ],

Reviewed By: @joelbeales

Differential Revision: D1437768
Move instead of deleting old server log

Summary: This should help debug server crashes that are only noticed
after a new server has already been started.

Reviewed By: @aryx

Differential Revision: D1438423