Add web docs for the instances data source (#431)

website/docs/d/instances.html.markdown

@@ -0,0 +1,76 @@
+---
+layout: "vultr"
+page_title: "Vultr: vultr_instances"
+sidebar_current: "docs-vultr-datasource-instances"
+description: |-
+  List information for Vultr instances.
+---
+
+# vultr_instances
+
+List information for Vultr instances.
+
+## Example Usage
+
+Get the information for all instances by `status`:
+
+```hcl
+data "vultr_instances" "active_instances" {
+  filter {
+    name   = "status"
+    values = ["active"]
+  }
+}
+
+// Print all labels for instances in the data source
+output "instances" {
+  value = data.vultr_instances.active_instances.instances[*].label
+}
+```
+
+## Argument Reference
+
+The following arguments are supported:
+
+* `filter` - (Required) Query parameters for finding instances.
+
+The `filter` block supports the following:
+
+* `name` - Attribute name to filter with.
+* `values` - One or more values filter with.
+
+## Attributes Reference
+
+The following attributes are exported:
+
+* `instances` - The list of instances which individually include the following:
+  * `os` - The operating system of the instance.
+  * `ram` - The amount of memory available on the instance in MB.
+  * `disk` - The description of the disk(s) on the server.
+  * `main_ip` - The server's main IP address.
+  * `vcpu_count` - The number of virtual CPUs available on the server.
+  * `region` - The region ID of the server.
+  * `date_created` - The date the server was added to your Vultr account.
+  * `allowed_bandwidth` - The server's allowed bandwidth usage in GB.
+  * `netmask_v4` - The server's IPv4 netmask.
+  * `gateway_v4` - The server's IPv4 gateway.
+  * `status` - The status of the server's subscription.
+  * `power_status` - Whether the server is powered on or not.
+  * `server_status` - A more detailed server status (none, locked, installingbooting, isomounting, ok).
+  * `plan` - The server's plan ID.
+  * `v6_network` - The IPv6 subnet.
+  * `v6_main_ip` - The main IPv6 network address.
+  * `v6_network_size` - The IPv6 network size in bits.
+  * `label` - The server's label.
+  * `internal_ip` - The server's internal IP address.
+  * `kvm` - The server's current KVM URL. This URL will change periodically. It is not advised to cache this value.
+  * `tag` - The server's tag.
+  * `tags` - A list of tags applied to the instance.
+  * `os_id` - The server's operating system ID.
+  * `app_id` - The server's application ID.
+  * `image_id` - The Marketplace ID for this application.
+  * `firewall_group_id` - The ID of the firewall group applied to this server.
+  * `features` - Array of which features are enabled.
+  * `backups_schedule` - The current configuration for backups 
+  * `hostname` - The hostname assigned to the server.
+  * `vpc2_ids` - A list of VPC 2.0 IDs attached to the server.