Remove inappropriate os.path.expandpath calls

This was prompted by 5c63955 which added an os.path.expandpath call to
the argument to --zvm-image.

I don't believe that we need to expand '~' and '~foo' in the command
line arguments to our scripts. That is the job of the shell and
normally works just fine with no effort on our part:

  % python -c 'import sys; print sys.argv' --some-arg ~/foo.txt
  ['-c', '--some-arg', '/home/mg/foo.txt']

The only problem is if users specify paths without a space:

  % python -c 'import sys; print sys.argv' --some-arg ~/foo.txt
  ['-c', '--some-arg=~/foo.txt']

If one insists on using no space, the correct way is to use an
environment variable:

  % python -c 'import sys; print sys.argv' --some-arg=$HOME/foo.txt
  ['-c', '--some-arg', '/home/mg/foo.txt']

This is consistent with how other tools such as sed and git works:

  % echo 's/foo/bar/' > ~/test.sed
  % echo hello foo | sed --file=~/test.sed
  sed: couldn't open file ~/test.sed: No such file or directory

  % echo 'commit msg' > ~/msg.txt
  % git commit --file=~/msg.txt
  fatal: could not read log file '~/msg.txt': No such file or directory

Paths read from configuration files (where there is no shell involved)
can be run through os.path.expanduser.
Avoid unnecessary os.path.abspath call for zvsh.cfg

Since we don't change directory at runtime, there is no need to give
absolute paths to ConfigParser.
zvsh: move os.path.abspath calls to where they're needed

When an application doesn't change it's current working directory, I
prefer to delay calls to os.path.abspath until they're really needed.
The advantage of this is that you get cleaner error messages, e.g.,
"cannot load 'foo'" instead of "cannot load '/home/you/foo'".
Merge pull request #18 from mgeisler/remove-expanduser-abspath

Remove some expanduser and abspath calls