Move Library Manager to separate group

docs/userguide/index.rst

@@ -59,7 +59,6 @@ Commands
     cmd_boards
     cmd_ci
     cmd_init
-    platformio lib <lib/index>
     platformio platforms <platforms/index>
     cmd_run
     cmd_serialports

docs/userguide/lib/index.rst

@@ -9,11 +9,20 @@
     See the License for the specific language governing permissions and
     limitations under the License.
 
-.. _userguide_lib:
+.. _librarymanager:
 
 Library Manager
 ===============
 
+*PlatformIO Library Manager* allows you to organize external embedded libraries.
+You can search for new libraries via
+
+* :ref:`Command Line interface <cmd_lib_search>`
+* `Web 2.0 Library Search <http://platformio.org/#!/lib>`_
+
+You don't need to bother for finding the latest version of library. Due to
+:ref:`cmd_lib_update` command you will have up-to-date external libraries.
+
 To print all available commands and options use:
 
 .. code-block:: bash