Make cli command case insensitive

iOS QGC capitalizes the command by default, so it's more convinient

flix/cli.ino

@@ -78,6 +78,8 @@ void doCommand(String str, bool echo = false) {
 		print("> %s\n", str.c_str());
 	}
 
+	command.toLowerCase();
+
 	// execute command
 	if (command == "help" || command == "motd") {
 		print("%s\n", motd);

gazebo/Arduino.h

@@ -52,6 +52,10 @@ public:
 		this->erase(0, this->find_first_not_of(" \t\n\r"));
 		this->erase(this->find_last_not_of(" \t\n\r") + 1);
 	}
+	void toLowerCase() {
+		std::transform(this->begin(), this->end(), this->begin(),
+			[](unsigned char c) { return std::tolower(c); });
+	}
 };
 
 class Print;