Fix template repository expansion for non-regular files

[lunny]

Only regular files will be expanded when creating a repository from a template repository.
Another change is to remove SSH public key comment in the authorized_keys file because their useless for authentication.

[wxiaoguang]

I don't think it is complete. At least:

1. put the username after the SSH key to make site admin know whose keys they are
2. filter out more paths like ".git"

[wxiaoguang]

Will rewrite