Remove cvs2svn chauvinism when referring to cvs2git etc.

In the documentation, example options files, etc. for each command,
use the name of that command rather than always using "cvs2svn".

git-svn-id: http://cvs2svn.tigris.org/svn/cvs2svn/trunk@5415 be7e6eca-30d4-0310-a8e5-ac0d63af7087
By default, store temporary files in the standard location.

Change the default for --tmpdir from "cvs2svn-tmp" to the result of
tempfile.mkdtemp(), which follows the usual convention for temporary
files (e.g., trying $TMPDIR, $TEMP, $TMP, then defaulting to a
platform-specific standard location).

Most of the effort of this patch is adjusting the documentation.

git-svn-id: http://cvs2svn.tigris.org/svn/cvs2svn/trunk@5416 be7e6eca-30d4-0310-a8e5-ac0d63af7087