Add docs for include/exclude in recorder (#1714)

Basically a copy of #1539, but with the changes requested (and some extra information copied from the history component).

source/_components/recorder.markdown

@@ -28,16 +28,65 @@ recorder:
 Configuration variables:
 
 - **purge_days** (*Optional*): Delete events and states older than x days.
+- **exclude** (*Optional*): Configure which components should be excluded from recordings.
+  - **entities** (*Optional*): The list of entity ids to be excluded from recordings.
+  - **domains** (*Optional*): The list of domains to be excluded from recordings.
+- **include** (*Optional*): Configure which components should be included in recordings. If set, all other entities will not be recorded.
+  - **entities** (*Optional*): The list of entity ids to be included from the history.
+  - **domains** (*Optional*): The list of domains to be included from the history.
 - **db_url** (*Optional*): The URL which point to your database. 
 
 
+Define domains and entities to `exclude` (aka. blacklist). This is convenient when you are basically happy with the information recorded, but just want to remove some entities or domains. Usually these are entities/domains which do not change (like `weblink`) or rarely change (`updater` or `automation`).
+
 ```yaml
-# Example configuration.yaml entry
+# Example configuration.yaml entry with exclude
 recorder:
   purge_days: 5
   db_url: sqlite:///home/user/.homeassistant/test
+  exclude:
+    domains:
+      - automation
+      - weblink
+      - updater
+    entities:
+      - sun.sun   # Don't record sun data
+      - sensor.last_boot
+      - sensor.date
 ```
 
+Define domains and entities to record by using the `include` configuration (aka. whitelist). If you have a lot of entities in your system and your `exclude` lists possibly get very large, it might be better just to define the entities or domains to record.
+
+```yaml
+# Example configuration.yaml entry with include
+history:
+  include:
+    domains:
+      - sensor
+      - switch
+      - media_player
+```
+
+Use the `include` list to define the domains/entities to record, and exclude some of them with in the `exclude` list. This makes sense if you for instance include the `sensor` domain, but want to exclude some specific sensors. Instead of adding every sensor entity to the `include` `entities` list just include the `sensor` domain and exclude the sensor entities you are not interested in.
+
+```yaml
+# Example configuration.yaml entry with include and exclude
+history:
+  include:
+    domains:
+      - sensor
+      - switch
+      - media_player
+  exclude:
+    entities:
+     - sensor.last_boot
+     - sensor.date
+```
+
+If you only want to hide events from e.g. your history, take a look at the [`history` component](/components/history/). Same goes for logbook. But if you have privacy concerns about certain events or neither want them in history or logbook, you should use the `exclude`/`include` options of the `recorder` component, that they aren't even in your database. That way you can save storage and keep the database small by excluding certain often-logged events (like `sensor.last_boot`).
+
+## Custom database engines
+
 | Database engine | `db_url`                                                 | 
 | :---------------|:---------------------------------------------------------|
 | SQLite          | `sqlite:///PATH/TO/DB_NAME`                              |