index.add: added index path rewrite functionality, which allows to store a different path in the index than the actual one on disk ( from which the object will be created )

Fixed bug the way newlines were handled, which  hopefully fixes occasional hangs as well. It works fine with git 1.7.1
Most of the changes are due to the tab-space conversion - its weird once more as I thought it was all in spaces before ... .

Author: Byron