some improvements to ocs-iso

Hello,

The attached patch handles several issues:
1. Typo. It says "$0 wll add that" instead of 'will'.
2. Temporary files are created in ./ if it is writable. I'm using a cifs folder which is writable, but for some reason the folders created using ocs-iso are not deleted. Anyway, I'm not sure why this is necessary. CZ live doesn't take much space anyway, so in most cases it should work on /tmp
3. Why use cd and then cp to . ?
4. Follow symbolic links. This allows creating a temp image (i.e. for changing some of the files while keeping the image files as symbolic links)