Make installation directories more flexible

In accordance with the GNU directory variables:
https://www.gnu.org/software/make/manual/html_node/Directory-Variables.html

Signed-off-by: Michael Wild <michael.wild@andritz.com>
Create destination directories in install target

Signed-off-by: Michael Wild <michael.wild@andritz.com>
Merge pull request #3 from themiwi/master

Fix install target to create the destination directories if they don't exist.