* adds proxy_url support,
adds proxy_url to the dockerswarm, eureka, kubernetes and consul service discovery,
adds proxy_url to the scrape_config for targets scrapping,
http based proxy is supported atm,
https://github.com/VictoriaMetrics/VictoriaMetrics/issues/503
* fixes imports
* adds consul watch api,
it must reduce load on consul service with blocking wait requests,
changed discoveryClient api with fetchResponseMeta callback.
* small fix
* fix after master merge
* adds watch client at discovery utils
* fixes consul watcher,
changes namings,
fixes data race
* small typo fix
* sanity fix
* fix naming and service node update
* Add omitempty for DisableCompression and DisableKeepAlive fields in ScrapeConfig
* Add omitempty annotation to all the default/optional values
* Fix annotations after review