ZVISION: Remove dead code
ZVISION: Use the search manager to open files in console commands
ZVISION: Remove dead code, and fix bad usage of assert()

Since some compilers, like MSVC, strip out asserts in non-debug builds,
it's a bad idea to perform active commands within assert() statements.
In this particular case, the engine would attempt to open a file in an
assert statement
ZVISION: Document where MIDI commands are used
ZVISION: Move the menu code together with the other scripting code
ZVISION: Normalize and cleanup all the menu-related enums