Handle avatar when it is passed as an argument in cli/config

[Kronopt]

As of right now, if the avatar path is passed as argument, the bot tries to edit its avatar every time it logins.
This can incur in too many avatar edits if the bot is restarted many times in a short period of time.

To fix, bot should check if the avatar in the path given as argument is the same as the current bot avatar.
Must download current avatar, hash it and compare hashes with the local avatar image

[Kronopt]

get bot avatar.
discord api image data.

• Extensions should be limited to those allowed by the discord api. Try to convert image extension to one of those allowed by discord (using Pillow) and throw error if that's not possible.
• Convert image size to the closest power of 2 between 16 and 4096
• Download existing bot avatar (with the same size as the converted one) and check to see if the images are equal. Only upload a new avatar if they are different.

[Kronopt]

Maybe it would be better to catch the error related to too many avatar changes and then just schedule the avatar change for sometime later.
Maybe the error message has some sort of time until avatar can be changed again?