check for windows version (32 or 64 Bits)

Starting the wrong installer will create a warning and
abort the installation.

Fixes #87: Winbareos installer 64 bit does not check, if windows is 64 bit

This patch should also set the right installation dir
for the different windows Versions.
( Program Files / Program Files (x86)

Signed-off-by: Marco van Wieringen <marco.van.wieringen@bareos.com>