Nmakefile: Add default flags and add command to add the manifest to .exe

Nmakefile: Add default flags and add command to add the manifest to .exe

The manifest is disabled for now, but once we fix the resolution we
should enable it.

to test:
nmake /f Nmakefile factor.exe.manifest

Right now the UI looks tiny if you compile for the factor.exe and
include the manifest.

Lastly, sorry for the WIP but it seems pretty harmless and has been
sitting in a branch for almost three years.