text: Title: --no Option for Aim Init, Do not Clear Existing Repo if it Exists
  Body: Happy to write a PR for this if we agree it helps.
  
  ## 🚀 Feature
  
  An "-n" or "--no" option for `aim init`, so that it only creates a new repo if one does not already exist.
  
  ### Motivation
  
  While running Aim in Kubernetes, I need to run aim init --repo /aim to make sure there is a repo for aim; however, since I have persistent storage, I would rather the --init option leave the repo intact if it already exists. Since this is happening in a container, I cannot answer "no" to the prompt.
  
  ### Pitch
  
  There is already a "-y" or "--yes" option, I'm thinking of just adding "-n" or "--no" option.
  
  ### Alternatives
  
  1. init's default could be set to initialize the repo only if it is not present.
  2. There could be an entirely different command "soft-init" or maybe a option "--soft" to achieve the same effect.
  I'm sure there are other alternatives that I have not thought of..
  