Drop empty documentation sections

... and fix the invalid installation guide to avoid confusions.

Tempest plugins are developed for testing so detailed documentation is
not usually needed.

Change-Id: I9632a02b96e02b69e6592f731c214d771218fcdf
diff --git a/doc/source/index.rst b/doc/source/index.rst
index 9455dcb..2da05ee 100644
--- a/doc/source/index.rst
+++ b/doc/source/index.rst
@@ -13,14 +13,8 @@
    :maxdepth: 2
 
    readme
-   install/index
-   library/index
+   installation
    contributor/index
-   configuration/index
-   cli/index
-   user/index
-   admin/index
-   reference/index
 
 Indices and tables
 ==================