Remove 'legend' arg from add_TA() and add_Series()

The 'legend' argument only supported the "auto" value. I tried to pass
user-supplied 'legend' values through the plotting functions, but it
didn't work seamlessly like it does when passing the 'name' argument.

Move the 'name' argument to the location of the 'legend' argument to
handle the case where the user explicitly provided "auto" as an unnamed
value for the 'legend' argument. For example:

    add_TA(x, NULL, NA, "auto")

See #377.

R/chart_Series.R

@@ -415,17 +415,27 @@ function(x,
          type = "candlesticks",
          order = NULL,
          on = NA,
-         legend = "auto",
-         theme = NULL,
          name = NULL,
+         theme = NULL,
          ...)
 {
   lenv <- new.env()
-  if(is.null(name)) {
+
+  if(is.null(name) || isTRUE(name == "auto")) {
+    # Checking for `name == "auto"` handles the case where the user explicitly
+    # provided "auto" for the 5th argument. The 5th argument used to be
+    # `legend = "auto"`, but only "auto" was supported.
     name <- deparse(substitute(x))
   }
   lenv$name <- name
-  lenv$plot_series <- function(x, series, type, ...) {
+
+  lenv$plot_series <- function(x, series, type, ..., legend = NULL) {
+    # The 'legend = NULL` argument was added to remove `legend` from `...` to
+    # suppress this warning:
+    ##    Warning message:
+    ##    In plot.xy(xy.coords(x, y), type = type, ...) :
+    ##      "legend" is not a graphical parameter
+
     # vertical grid lines
     if(FALSE) theme <- NULL
     segments(axTicksByTime2(xdata[xsubset]),
@@ -440,8 +450,8 @@ function(x,
   lenv$xdata <- x
   # map all passed args (if any) to 'lenv' environment
   mapply(function(name,value) { assign(name,value,envir=lenv) }, 
-        names(list(x=x,type=type,order=order,on=on,legend=legend,...)),
-              list(x=x,type=type,order=order,on=on,legend=legend,...))
+        names(list(x=x,type=type,order=order,on=on,...)),
+              list(x=x,type=type,order=order,on=on,...))
   exp <- parse(text=gsub("list","plot_series",
                as.expression(substitute(list(x=current.chob(),type=type,series=get("x"), ...)))),
                srcfile=NULL)
@@ -496,19 +506,29 @@ add_TA <-
 function(x,
          order = NULL,
          on = NA,
-         legend = "auto",
+         name = NULL,
          yaxis = list(NULL, NULL),
          col = 1,
          taType = NULL,
-         name = NULL,
          ...)
 {
   lenv <- new.env()
-  if(is.null(name)) {
+
+  if(is.null(name) || isTRUE(name == "auto")) {
+    # Checking for `name == "auto"` handles the case where the user explicitly
+    # provided "auto" for the 4th argument. The 4th argument used to be
+    # `legend = "auto"`, but only "auto" was supported.
     name <- deparse(substitute(x))
   }
   lenv$name <- name
-  lenv$plot_ta <- function(x, ta, on, taType, col=col,...) {
+
+  lenv$plot_ta <- function(x, ta, on, taType, col=col, ..., legend=NULL) {
+    # The 'legend = NULL` argument was added to remove `legend` from `...` to
+    # suppress this warning:
+    ##    Warning message:
+    ##    In plot.xy(xy.coords(x, y), type = type, ...) :
+    ##      "legend" is not a graphical parameter
+
     xdata <- x$Env$xdata
     xsubset <- x$Env$xsubset
     if(all(is.na(on))) {
@@ -539,9 +559,9 @@ function(x,
   lenv$xdata <- x
   # map all passed args (if any) to 'lenv' environment
   mapply(function(name,value) { assign(name,value,envir=lenv) }, 
-        names(list(x=x,order=order,on=on,legend=legend,
+        names(list(x=x,order=order,on=on,
                    taType=taType,col=col,...)),
-              list(x=x,order=order,on=on,legend=legend,
+              list(x=x,order=order,on=on,
                    taType=taType,col=col,...))
   exp <- parse(text=gsub("list","plot_ta",
                as.expression(substitute(list(x=current.chob(),