git init should not include files in an existing raw/ dir, in its search for large binary files

If a raw/ dir already exists, then skip looking at those files.
Ver 0.7.6

Files that are in ignorefiles should also be ignored in the search for large files, because they will not be added to the initial git repo (i.e. they better not be added).

"mkdir raw" should be skipped if it exists.

Existing files in raw/ should not be replaced with any moves. An error should be thrown.
