Improvements for Attachment 5 (BAT) scripts in OCCT installation

The attached file contains improved Attachment 5 (BAT) script aimed to replace the script
created by the OCCT installer in ros subdirectory of Open CASCADE installation
on Windows.

The improvements are intended to make the script more universal:

- The variable CASROOT is set only if not defined already.

- The CASROOT is set equal to the directory where this file emv.bat is located,
using Windows batch variable substitution rather than explicit string. Thus
path of the directory is not embedded into Attachment 5 (BAT); this allows to access the
OCCT installation by path different from the installation path (e.g. from
network or after moving of OCCT installation)

- The possibility to have several builds of OCCT libraries (e.g. Debug build
put in "bind" subdirectory) is supported, by using optional variable CASDEB. If
this variable is defined, it is added as suffix to "bin" directory name in PATH.

- The variable CSF_GraphicShr is now defined without path, so TKOpenGl will be
effectively searched by PATH