The file discovery should only stop the watcher if it has been created
otherwise it may trigger a segmentation fault.

Decouple the discovery and refactor the retrieval package

The docs suggest that alert templating only works in the summary and
description annotation fields. Some testing and a review of the code
suggests this is no longer true and that you can template any
annotation field.

main.go integration test for Startup interrupting.

Signed-off-by: Krasi Georgiev <krasi.root@gmail.com>

split the groupsMerge function to set and get
other small nits

handle errors with invalid scrape config

remove some select state that is most likely obsoleete and hoepfully doesn't braje anything :)
merge targets will sort by Discoverer name so we can have consistent tests for the maps.

scrape pool doesn't rely on context as Stop() needs to be blocking to prevent Scrape loops trying to write to a closed TSDB storage.

Otherwise it defaults to 2, and Go will close extra connections as
soon as a request is finished.
See https://github.com/golang/go/issues/13801

As discussed generally consider SDs as unstable, as realistically they
are never going to be. Drop the words "experimental/beta" from most
places in the docs, as users are getting the wrong impression from this.

openstack_sd_config requires a 'role' parameter which wasn't documented.

Fixes https://github.com/prometheus/docs/issues/681

Change wrong URL for remote.proto

Resolves an issue where rendered markdown was incorrect.

Added service discovery view showing labels before and after relabelling

Currently when sending alerts via the go routine within `sendAll`, the value
of `ams` is not passed to the routine, causing it to use the updated value of `ams`.

Example config:

```
alerting:
  alertmanagers:
    - basic_auth:
        username: 'prometheus'
        password: 'test123'
      static_configs:
      - targets:
        - localhost:9094
    - static_configs:
      - targets:
        - localhost:9095
```

In this example alerts sent to `localhost:9094` fail with:

```
level=error ts=2017-10-12T10:03:53.456819948Z caller=notifier.go:445
component=notifier alertmanager=http://localhost:9094/api/v1/alerts
count=1 msg="Error sending alert" err="bad response status 401
Unauthorized"
```

If you change the order to be:

```
alerting:
  alertmanagers:
    - static_configs:
      - targets:
        - localhost:9095
    - basic_auth:
        username: 'prometheus'
        password: 'test123'
      static_configs:
      - targets:
        - localhost:9094
```

It works as expected.

This commit changes the behavour so `ams` is passed to the go routine so
`n.sendOne` uses the appropriate `http.Client` details.

Make the date returned by snapshot script friendly

Deprecate DeduplicateSeriesSet() in favor of NewMergeSeriesSet().

net.Listener converts 0.0.0.0 to :: which fails for hosts where IPv6 is
disabled. This change uses the original listen address parameter instead
of grpcl.Addr().String().

Fixes #3564