#164 add searchGameComment() function

[Paolo Casaschi]

Add searchGameComment(searchExpression, backward) function to scan current game for searchExpression and move to ply with matching comment.

Consider interaction with existing searchPgnGame()

[Paolo Casaschi]

basic implementation:

function searchGameComment(searchExpression, backward) {
  var searchExpressionRegExp = new RegExp(searchExpression, "im");
  var keepGoing = 1;
  for (var vv = 0; vv < numberOfVars && keepGoing; vv++) {
    for (var ii = StartPlyVar[vv]; ii < PlyNumberVar[vv] && keepGoing; ii++) {
      if (strippedMoveComment(ii, vv).match(searchExpressionRegExp)) { 
        GoToMove(ii, vv);
        keepGoing = 0;
      }
    }
  }
}

need to add:
- backward option
- start from current position and loop (instead of starting from the beginning)
- return value