Renamed some variables to improve code readability

Author: cmaglie

arduino/cores/packagemanager/loader.go

@@ -453,20 +453,19 @@ func (pm *PackageManager) loadBoards(platform *cores.PlatformRelease) error {
 	}
 
 	boardsTxtPath := platform.InstallDir.Join("boards.txt")
-	boardsProperties, err := properties.LoadFromPath(boardsTxtPath)
+	allBoardsProperties, err := properties.LoadFromPath(boardsTxtPath)
 	if err != nil {
 		return err
 	}
 
 	boardsLocalTxtPath := platform.InstallDir.Join("boards.local.txt")
-	if localProperties, err := properties.SafeLoadFromPath(boardsLocalTxtPath); err == nil {
-		boardsProperties.Merge(localProperties)
+	if boardsLocalProperties, err := properties.SafeLoadFromPath(boardsLocalTxtPath); err == nil {
+		allBoardsProperties.Merge(boardsLocalProperties)
 	} else {
 		return err
 	}
 
-	propertiesByBoard := boardsProperties.FirstLevelOf()
-
+	propertiesByBoard := allBoardsProperties.FirstLevelOf()
 	if menus, ok := propertiesByBoard["menu"]; ok {
 		platform.Menus = menus
 	} else {
@@ -479,7 +478,7 @@ func (pm *PackageManager) loadBoards(platform *cores.PlatformRelease) error {
 	skippedBoards := []string{}
 	for boardID, boardProperties := range propertiesByBoard {
 		var board *cores.Board
-		for key := range boardProperties.AsMap() {
+		for _, key := range boardProperties.Keys() {
 			if !strings.HasPrefix(key, "menu.") {
 				continue
 			}