General cleanup and fixes for tomcat7 and PyXDG errors, adding a /downloads location to Dockerfile

[dragonfyre13]

Janitorial:

• Some general cleanup tasks on logs that were left in place when the original tar file was compiled
• Renamed the gzipped tar file to "tar.gz" rather than "tar"

Bug Fix:

• PyXDG errors in the log after starting, resolves a "black screen" issue with JDownloader2 immediately following installation on some systems.
• Tomcat7 cache directory issues given a missing /cache/tomcat7 location. Greatly speeds up starting the container after the first time, may speed up usage while container is running (not sure what specifically it's used for beyond temp cache for war contents across tomcat restarts)

Feature Add:

• Added "/downloads" to Dockerfile, right now the user is forced to put downloads within the /config directory, however in many cases for unraid /downloads may well be preferred on the array itself while the /config may be better held on the cache drive (or similar).

[aptalca]

Thanks for the PR. Some comments and questions:
The tomcat folder creation should really be added to the dockergui baseimage that this image uses: https://github.com/linuxserver/dockergui/tree/x11rdp1.3

Missing pyXDG is likely a baseimage issue as well (not 100% sure on this) and should be corrected there. Could you elaborate more on this issue?

/downloads location does not have to be exposed in the Dockerfile. That exposure is only for container to container communication within a separate docker network. You can always map a folder through docker run/create by adding -v /path/to/folder:/downloads, which will create a /downloads folder inside the image and map it to the folder on the host.

I'm not super comfortable with modifications to the tar binary (no offense). I probably shouldn't have used a tar binary myself in the first place. Ideally, I would have pulled the java source directly during build but took the easy way out I guess.