Docker - Duniter wrapper + Entrypoint can survive a config / peers.db loss

See merge request !1387

Add new Docker environment variable: `DUNITER_PEER_HOST` (default to
`DUNITER_SYNC_HOST`).

When `conf.json` doesn't exist and `DUNITER_PEER_HOST` designs a remote
node, bootstrap currency parameters from this node into the configuration
file.

When `peers.db` doesn't exist and `DUNITER_PEER_HOST` designs a remote node,
use `sync $DUNITER_SYNC_HOST --only-peers` to have its endpoints into
`peers.db`.

And force option '--home /var/lib/duniter' in the wrapper when not given.

It should help when running an interactive shell into the instance.

feat(bma): fill field time with receivedTime for pending txs

See merge request !1386

fix(sync): when called with --only-peers

See merge request !1385

When 'sync' is called with option '--only-peers', the path to function
'RemoteSynchronizer.getPeers()' is not the same as the default.

In this case we need to ensure that 'init()' was properly called and
proceed without a watcher.

feat(bma): configure with env var

See merge request !1382

Docker: move config back to volume /var/lib/duniter and other minor changes

See merge request !1381

Moving `conf.json` from volume `/var/lib/duniter` to volume `/etc/duniter`
was a mistake. It creates to much many corner cases where one can lose
their configuration file.

This commit partly reverts fd0bbe67 by bringing conf.json back into volume
`/var/lib/duniter`.

Was /duniter/duniter.

Spare one process.

And link duniter binary as /usr/bin/duniter.

little closer to conventionalcommits.org