Build improvements to add vs2012 support, and rename ACMLROOT to standard ACML_ROOT syntax

Modifications to the cmake build files to add support for microsoft vs2012 compilers
Build break change by renaming ACMLROOT to ACML_ROOT, but it is about time that the environment variable reflected CMAKE convention by using underscores.  This enables the 'grouped' checkbox in the cmake-gui to properly group the ACML_ROOT variable