Small fixes to 'data streams' section (#508)

This is just a small follow-up PR to the earlier
#490

It:
- Removes the "Index types" page (all content in that page is already
captured in the "index basics" page that Wajiha assembled
- Moves the "Logs data stream" page to be parallel with "Time series
data stream", rather than nested under it (a mistake from my earlier
PR).

I also planned to add a note about "data streams" to the "Index basics"
page, but I see Wajiha already has that one covered. :-)

Closes: elastic/docs-projects#324

Author: kilfoyle

manage-data/data-store.md

@@ -11,4 +11,6 @@ The documentation in this section details how {{es}} works as a _data store_ sta
 
 Then, learn how these documents and the fields they contain are stored and indexed in [Mapping](/manage-data/data-store/mapping.md), and how unstructured text is converted into a structured format that’s optimized for search in [Text analysis](/manage-data/data-store/text-analysis.md).
 
-You can also read more about working with {{es}} as a data store including how to use [index templates](/manage-data/data-store/templates.md) to tell {{es}} how to configure an index when it is created, how to use [aliases](/manage-data/data-store/aliases.md) to point to multiple indices, and how to use the [command line to manage data](/manage-data/data-store/manage-data-from-the-command-line.md) stored in {{es}}.
+You can also read more about working with {{es}} as a data store including how to use [index templates](/manage-data/data-store/templates.md) to tell {{es}} how to configure an index when it is created, how to use [aliases](/manage-data/data-store/aliases.md) to point to multiple indices, and how to use the [command line to manage data](/manage-data/data-store/manage-data-from-the-command-line.md) stored in {{es}}.
+
+If your use case involves working with continuous streams of time series data, you may consider using a [data stream](./data-store/data-streams.md). These are optimally suited for storing append-only data. The data can be accessed through a single, named resource, while it is stored in a series of hidden, auto-generated backing indices.

manage-data/data-store/index-types.md

@@ -4,7 +4,6 @@ toc:
   - file: data-store.md
     children:
       - file: data-store/index-basics.md
-      - file: data-store/index-types.md
       - file: data-store/data-streams.md
         children:
           - file: data-store/data-streams/set-up-data-stream.md
@@ -19,7 +18,7 @@ toc:
               - file: data-store/data-streams/run-downsampling-manually.md
               - file: data-store/data-streams/run-downsampling-using-data-stream-lifecycle.md
               - file: data-store/data-streams/reindex-tsds.md
-              - file: data-store/data-streams/logs-data-stream.md
+          - file: data-store/data-streams/logs-data-stream.md
       - file: data-store/mapping.md
         children:
           - file: data-store/mapping/dynamic-mapping.md