make default permissions for /config /data /log tunable
variable renaming for clarity
More relevant completion message
Allow custom file ownership/permissions to config files.

PERMISSIONS_EXCEPTIONS holds a string, separated by spaces, of
files and/or directories to chmod and chown. The format for a single
entry is:

{file/folder path}:{octal mode}[:user][:group]

fixes radial/docs#2
Update README for PERMISSIONS_* env var instructions