Add option to enable GNU Install Dirs

The way issue 15 was solved made it very difficult to install console_bridge system-wide on a distribution that does not use /usr/lib as the library installation path. This patch is a better way to solve the issue 15: rather than just nuking the GNUInstallDirs logic from orbit, it adds a configuration switch to optionally enable the functionality, leaving it disabled by default so ROS doesn't break.