Improve configuration docs with common changes and start/stop/restart directions (netdata#10415)

* Finish new common config doc, delete old one

* Small tweak to blockquote

* Add new files

* Fix broken links

* Fix one more broken link

* Copyedits and improvements

* Fix broken link

* Re-add common config doc

* service -> systemctl

* Reverse systemctl order

* Add mention of .conf files in health.d

* Add mention of minimum global update every

Author: joelhans

daemon/config/README.md

@@ -67,7 +67,8 @@ Please note that your data history will be lost if you have modified `history` p
 | plugins directory|`"/usr/libexec/netdata/plugins.d" "/etc/netdata/custom-plugins.d"`|The directory plugin programs are kept. This setting supports multiple directories, space separated. If any directory path contains spaces, enclose it in single or double quotes.|||
 | memory mode         | `dbengine` | `dbengine`: The default for long-term metrics storage with efficient RAM and disk usage. Can be extended with `page cache size` and `dbengine disk space`. <br />`save`: Netdata will save its round robin database on exit and load it on startup. <br />`map`: Cache files will be updated in real-time. Not ideal for systems with high load or slow disks (check `man mmap`). <br />`ram`: The round-robin database will be temporary and it will be lost when Netdata exits. <br />`none`: Disables the database at this host, and disables health monitoring entirely, as that requires a database of metrics. |
 | page cache size     | 32         | Determines the amount of RAM in MiB that is dedicated to caching Netdata metric values. |||
-| dbengine disk space | 256        | Determines the amount of disk space in MiB that is dedicated to storing Netdata metric values and all related metadata describing them |||
+| dbengine disk space | 256        | Determines the amount of disk space in MiB that is dedicated to storing Netdata metric values and all related metadata describing them. |||
+| dbengine multihost disk space | 256        | Same functionality as `dbengine disk space`, but includes support for storing metrics streamed to a parent node by its children. Can be used in single-node environments as well. |||
 | host access prefix||This is used in docker environments where /proc, /sys, etc have to be accessed via another path. You may also have to set SYS_PTRACE capability on the docker for this work. Check [issue 43](https://github.com/netdata/netdata/issues/43).|
 | memory deduplication (ksm)|`yes`|When set to `yes`, Netdata will offer its in-memory round robin database to kernel same page merging (KSM) for deduplication. For more information check [Memory Deduplication - Kernel Same Page Merging - KSM](/database/README.md#ksm)|||
 | TZ environment variable|`:/etc/localtime`|Where to find the timezone|||