closes #1348

* return partition stat alongside disk stat from disk usage method, and report device name (minus /dev/) as a tag in disk stats

* update system/disk tests to include new partition stat return value from disk usage method calls

* update changelog for #1807 (use device name instead of path to report disk stats)

Signed-off-by: Pierre Fersing <pierre.fersing@bleemeo.com>

On linux, the cpu timer counters of user and nice include the respective guest and guest_nice counters. This results in improper calculation of percentages.

Please see:
https://github.com/torvalds/linux/blob/447976e/kernel/sched/cputime.c#L169
https://lists.linuxfoundation.org/pipermail/virtualization/2009-August/013459.html
https://github.com/giampaolo/psutil/pull/940

main reasons behind this:
- make adding/removing tags cheap
- make adding/removing fields cheap
- make parsing cheaper
- make parse -> decorate -> write out bytes metric flow much faster

Refactor serializer to use byte buffer

The old gonuts fork has no License and has not seen any commits
differing from the original project, while the original has seen some
activity, even if low.

Having no license is a problem for distributors, as by default, such
projects are undistributable.

* [plugins] rabbitmq input plugin: add non default http timeouts

* update CHANGELOG.md

* Export IopsInProgress

* Export IopsInProgress

* Export IopsInProgress

* Trim null characters in Value data format

Some producers (such as the paho embedded c mqtt client) add a null
character "\x00" to the end of a message.  The Value parser would fail on
any message from such a producer.

* Trim whitespace and null in all Value data formats

* No unnecessary reassignments in Value data format parser

* Update change log for Value data format fix

* added connection Timeout parámeter, basic HTTP autentication and HTTP support with Sslskipverify option

* updated README.md

* added optional SSL config , changed timeout name and type , and other minor fixes

* added some code style improvements

* Update README.md

* Cache and expire metrics for prometheus output

* Fix test

* Use interval.Duration

* Default prometheus expiration interval to 60s

* Update changelog

* patching udp_listener for fun

updating with errcode

adding debug flags to temp msgs

moving from debug to info

* updating PR 1883 based on feedback

Fix single quote parsing of TOML durations

closes #2023

- fully document aggregator and processor plugins
- improve readme.md

closes #1989

Also don't use named returns in fetchNamespaceMetrics since it's
non-standard for the rest of the codebase.

closes #1564

also add unit and benchmark tests

I think this is a copy paste bug? ;-)

primarily for a fix in Windows network counter getting code

closes #1949