extract volatiles for at into own bbappend
Update nginx bbappend for /var/lib move

* when bind-mount /var/lib instead of union-fs, /var/lib/nginx must exists
  before nginx is started
* rename bbappend file to be save on upgrades
acquire /var/lib r/w access via mount-bind instead

depreciate union-fs for /var/lib
move hp2 user into dedicated recipe

including correct volatiles settings for logging
on update, wipe out .var_lib
add helper for hard-reseting files in r/w of union

Because of the nature of the beast, you can't unlink files in the underlying
r/w filesystem of a unionfs. In rare cases where starting fresh is a viable
case, system reset is required and a list of file system entries to be
removed must be processed before unionfs is mounted.

Misuse can damage your file systems and lead to continuous kernel panics.
Use with caution!