Concept of user and implementation of STAT command

[omikuji]

Hello Koenw! Thank you for replying the other day!

I added U for the purpose of giving user information to each action. By implementing this, you can change the behavior for each user. (For example, change the upload path prefix for each user.)

In addition, implemented the STAT command. For the time being, i made simple ones. I would like to expand it in the future!

Thank you :)