Remove CORES, add hot_add capability

There is no need to add multiple devices per CORE as zram is natively multi-core capable now (since quite some time). So just always add a single swap device.

The old way assumed there was no zram device before and the module was not loaded yet, which is not a reasonable assumption. So make use of zram's hot_add functionality and add a new device in case one already existed.

Protect against starting zramswap multiple times

All while trying to keep the changes at a minimum.

Only the latest patch contains real changes, the rest updates your packaging branch to master