Adding systemd service for bitcoind, to provide for a simpler
out-of-the-box experience.
Configuration file is /etc/bitcoin/bitcoin.conf. This file is a
copy of the sample configuration file.
The service user 'bitcoin' is added during install. Its homedir
is in '/var/lib/bitcoin'.
bitcoind.service is disabled by default to allow the user to
configure it, before starting it the first time.
On package purge, the 'bitcoin' user as well as its homedir is
left intact, to not accidentally remove a wallet or something of
equal importance. Instead the user is presented with information
on how to perform the cleanup manually, after making sure all
important data has been backed up.
This:
* Partially reverts 9f68ed6 (which fixed spelling in a changelog,
though generally changelogs should be append-only).
* Disables UPnP support (PPA has not had it for a while, and I
still don't trust miniupnpc, plus it seems uneccessary - its
been a while since we needed to care about Bitcoin-Qt home users
getting their inbound ports auto-mapped).
* Enables ZMQ.
* Forces GUI to Qt4 to fix various issues people have been seeing
on Ubuntu and elsewhere with Qt5.
* Reverts 70899d70b (Bitcoin does not enable "instant payments",
not is transaction management "carried out collectively by the
network", for whatever "transaction management" means, finally
Bitcoin Core is not the only way to use the Bitcoin currency,
as seemingly implied in the description).
