docs: Update DigitalOcean resource pages

Specifically:

- User data is available in all regions, so remove the sentence saying
  to check for supported features in each region.

- Clarify domain vs. DNS record resources.

- Explain which DNS record types the `weight`, `port`, and `priority`
  arguments are applicable for.

website/source/docs/providers/do/r/domain.html.markdown

@@ -13,7 +13,7 @@ Provides a DigitalOcean domain resource.
 ## Example Usage
 
 ```
-# Create a new domain record
+# Create a new domain 
 resource "digitalocean_domain" "default" {
     name = "www.example.com"
     ip_address = "${digitalocean_droplet.foo.ipv4_address}"
@@ -43,4 +43,4 @@ Domains can be imported using the `domain name`, e.g.
 
 ```
 terraform import digitalocean_domain.mydomain mytestdomain.com
-```
+```

website/source/docs/providers/do/r/droplet.html.markdown

@@ -48,8 +48,6 @@ The following arguments are supported:
 * `tags` - (Optional) A list of the tags to label this droplet. A tag resource
    must exist before it can be associated with a droplet.
 * `user_data` (Optional) - A string of the desired User Data for the Droplet.
-   User Data is currently only available in regions with metadata
-   listed in their features.
 * `volume_ids` (Optional) - A list of the IDs of each [block storage volume](/docs/providers/do/r/volume.html) to be attached to the Droplet.
 
 ## Attributes Reference

website/source/docs/providers/do/r/record.html.markdown

@@ -3,17 +3,17 @@ layout: "digitalocean"
 page_title: "DigitalOcean: digitalocean_record"
 sidebar_current: "docs-do-resource-record"
 description: |-
-  Provides a DigitalOcean domain resource.
+  Provides a DigitalOcean DNS record resource.
 ---
 
 # digitalocean\_record
 
-Provides a DigitalOcean domain resource.
+Provides a DigitalOcean DNS record resource.
 
 ## Example Usage
 
 ```
-# Create a new domain record
+# Create a new domain 
 resource "digitalocean_domain" "default" {
     name = "www.example.com"
     ip_address = "${digitalocean_droplet.foo.ipv4_address}"
@@ -36,9 +36,10 @@ The following arguments are supported:
 * `domain` - (Required) The domain to add the record to
 * `value` - (Optional) The value of the record
 * `name` - (Optional) The name of the record
-* `weight` - (Optional) The weight of the record
-* `port` - (Optional) The port of the record
-* `priority` - (Optional) The priority of the record
+* `weight` - (Optional) The weight of the record, for SRV records.
+* `port` - (Optional) The port of the record, for SRV records.
+* `priority` - (Optional) The priority of the record, for MX and SRV
+   records.
 
 ## Attributes Reference