[Bf-codereview] Paths and Windows Installer Fixes (issue4529081)

[brechtvanlommel at gmail.com]

Latest change should fix issue with existing system script installation
in user configuration directory:

* Copy previous settings operator will not copy over system scripts to
2.58.
* 2.57 builds will use local path as user scripts directory in case user
path contains 2.57 system scripts from installer, until version is
bumped to 2.58.

http://codereview.appspot.com/4529081/