Add more concepts for servers

There still have some important concept in the docs, this patch adds
more to it.

blueprint complete-todo-in-api-concept-doc

Change-Id: I231f298d2c7ffa0736028db27fe54691ac4bd201

api-guide/source/server_concepts.rst

@@ -8,6 +8,10 @@ a physical machine or a container.
 Server status
 ~~~~~~~~~~~~~
 
+TODO: This section's content is old, we need to update the status list.
+The task_state and vm_state which expose to Administrator need description to
+help user to understand the difference.
+
 You can filter the list of servers by image, flavor, name, and status
 through the respective query parameters.
 
@@ -118,6 +122,12 @@ administrative password are guaranteed to be returned in the request.
 You can retrieve additional attributes by performing subsequent **GET**
 operations on the server.
 
+Server query
+~~~~~~~~~~~~
+
+TODO: We should introduce that there are multiple methods to filter the
+response of list servers.
+
 Server actions
 ~~~~~~~~~~~~~~~
 
@@ -300,6 +310,21 @@ of key-value pairs that can be supplied per server is determined by the
 compute provider and may be queried via the maxServerMeta absolute
 limit.
 
+Block Device Mapping
+~~~~~~~~~~~~~~~~~~~~
+
+TODO: Add some description about BDM.
+
+Scheduler Hints
+~~~~~~~~~~~~~~~
+
+TODO: Add description about how to custom scheduling policy for server booting.
+
+Server Consoles
+~~~~~~~~~~~~~~~
+
+TODO: We have multiple endpoints about consoles, we should explain that.
+
 Server networks
 ~~~~~~~~~~~~~~~