Major revamp

This is a major revamp, since it allow in-app updates. No more edge
hack.

It uses precompiled packages, easily created with build.sh script.
These packages are located in the /repository dir.

The docker container is in the /docker dir, so if you merge this, you
have to modify the Dockerfile path in the Docker Hub.

FIles:

build.sh - this file has two functions, one to compile the libpar2
package and other to compile nzbget.

nzbget-update-install.sh: this file is invoked by nzbget to download
the update. It will then create a /tmp/update.sh script that will be
used by the nzbget.sh to make the update.

package-info.json: this package have information about the existence of
updates, will be moved to the nzbget webui dir by firstrun.sh.

nzbget-update-info.json: this file have the updates info, and is
downloaded by nzbget. It’s address is set by the package-info.json file.