Removes unnecessary dependencies on sed, cp, and chmod

There are a number of CMake custom tasks that will cause *make* to fail on Windows after constructing MinGW makefiles.  Specifically, the tasks rely on UNIX-y commands: cp, sed, and chmod.  Most of the tasks are unnecessary, however.

The *cp* tasks should be using *${CMAKE_COMMAND} -E copy* per the CMake documentation for cross-platform support.

The *sed* tasks are straightforward text replacements.  CMake can handle these using *STRING* commands instead.

The *chmod* tasks are somewhat more problematic.  The *gtk-2-fortran-modscan* executable can be set with the proper permissions by setting *WORLD_EXECUTE* during install rather than using *chmod*.  The *run_all* script in *tests* is no longer marked as executable, however, as it isn't installed.  It's a bit of a problem.

These changes shouldn't adversely affect any other platforms.