Multi-user support + Init script

[artemkv]

I recently tried to use this helm chart and ran into some limitations. I made some improvements I needed in the fork. If you like them, please feel free to accept the pull request. If not, feel free to simply pick the pieces you liked.

Improvements:

• Included pull request fixing a missing indent in sftp-container resource definition (Fixed missing indent in sftp-container resource definition. #6)
• Support for multiple users having different passwords and mounting different paths on a persistent volume. This allows to configure 2 users, one for external, more limited access, and one for internal, less limited access
• Support for init script
• I also changed the default image to atmoz/sftp

[AmundsenJunior]

README should be updated to show that the fields under users are items in a list of users, not fields directly attached to users.