COMP: Update CLI shared library fix up rule to ensure CLI executable works

Before this commit, within extension, CLI executables were installed
in "cli-modules" folder whereas the CLI shared libraries were fixed
up in "lib/Slicer-4.2/cli-modules" folder. Doing so allowed either
CLI shared libraries or CLI executable without dependent library to be
loaded but *NOT* CLI executable depending on CLI shared library.

This was the cause of the issue and can be explained by the fact the
"@executable" expression is specific to the location of a the Slicer
executable itself. To allow a CLI executable to resolve its associated
shared library, this one had to be installed in a directory at the same
depth as the Slicer executable itself.

This commit ensure that both CLI executable and libraries will end up
in the same directory: "cli-modules" so that the CLI shared library can
be referenced by either the Slicer executable itself or a CLI executable.

This commit also centralized the place were the CLI module path are set.

See http://www.na-mic.org/Bug/view.php?id=3051
Fixes #3051