Remove cinch_add_application_directory and cinch_target_link_libraries

[junghans]

After the refactor cinch_add_application_directory and cinch_target_link_libraries don't do anything anymore, so we should mark them as deprecated (message(WARNING ...)) and remove them in the next version of cinch.

[charest]

@junghans I left them there because they print out a nice message. So they still do something!

[junghans]

@tuxfan : Do we need this message?

[junghans]

I would prefer using plain cmake functions.

[charest]

We probably don't, I can do it.