symbol handling.

List connections that have symbols.

in:
{
 "function": "Symbols/ListSymbolConns",
 "id": "some-text-or-number",
 "data": {
   "StartOffset": 0
 }
}
out:
{
 "function": "Symbols/ListSymbolConns",
 "id": "some-text-or-number",
 "status": 0,
 "data": {
  "Connections": [
   { "ConnectionName": "a", "ConnectionGroup": "b" },
   { "ConnectionType": ["S7"] }
  ],
  "Blocked": false
 }
}

List symbol directories of a connection.

in:
{
 "function": "Symbols/ListSymbolDirs",
 "id": "some-text-or-number",
 "data": {
   "ConnectionName": "a",
   "ConnectionGroup": "b",
   "ConnectionType": "S7",
   "StartOffset": 0
 }
}
out:
{
 "function": "Symbols/ListSymbolDirs",
 "id": "some-text-or-number",
 "status": 0,
 "data": {
  "Dirs": [
   { "DirName": "a" },
   ...
  ],
  "Blocked": false
 }
}

List symbols of a connection.

in:
{
 "function": "Symbols/ListSymbols",
 "id": "some-text-or-number",
 "data": {
   "ConnectionName": "a",
   "ConnectionGroup": "b",
   "ConnectionType": "S7",
   "StartOffset": 0
 }
}
out:
{
 "function": "Symbols/ListSymbols",
 "id": "some-text-or-number",
 "status": 0,
 "data": {
  "Symbols": [
   { "Name": "MySymbol" },
     "Syntax": "db10bbw12.5" },
     "Comment": "MyComment" },
   ...
  ],
  "Blocked": false
 }
}