Improve GENZH cmake option names

[xezon]

1

The GENZH_BUILD_ options are getting poluted which makes it more difficult to see the important targets.

The most important build options are

GENZH_BUILD_GENERALS
GENZH_BUILD_GENERALS_TOOLS
GENZH_BUILD_GENERALS_EXTRA
GENZH_BUILD_ZEROHOUR
GENZH_BUILD_ZEROHOUR_TOOLS
GENZH_BUILD_ZEROHOUR_EXTRA

I think they need to stand more alone without distractions.

And the other GENZH_BUILD options need renaming.

2

It would also be nice if the naming of

GENZH_GENERALS_INSTALL_PREFIX
GENZH_ZEROHOUR_INSTALL_PREFIX

would group them together.

To do that, they can be named

GENZH_INSTALL_PREFIX_GENERALS
GENZH_INSTALL_PREFIX_ZEROHOUR