[CMake] Overwiew CMake install commands

[Joachim Ziegler]

Brandon Van Every wrote:
> > As the docs say for all 3:
> > "Old installation command. Use the INSTALL command."
> > CMake has some legacy commands in the documentation.  Ignore them and
> > use the current recommended commands.

Yes, I've seen that and read the documentation of the new INSTALL
comand. It is still unlear to me in what case I should use what command.
(What is the conecuptual difference between a FILE and a TARGET? May a
TARGET consist of more than one files?)

And I still do not undestand the effect of these commands concerning a
"make package_source". Do they have any? If not, how can I fine-tune
what gets packaged into a package_source?

Regards,
Joachim