Added APT-Mirror package.

Added package to run a local debian/ubuntu repository. End user is responsible for linking the different spools to /var/services/web/ and schedule a daily update.
I've been using it for a few days now without any issue on cedarview. The package depends on gzip and wget (as the synology version of these program are... weird) but gzip won't compile on powerpc as the toolchains don't provide gcc>=4.2.