Add untargeted folder for specs

It was discussed at the Cinder Mid-Cycle that we
needed something to do with approved specs that were
still relevant but not being worked.  The recommendation
was to add an untargeted folder like the one that Glance
uses.  This patch does this.

I also discovered that the last two sections in
the index page were not displaying due to
incorrect RST format.  This patch also fixes
that.

Change-Id: I3f909742501ab3a3f36ba9eee4ede0b814f76f2d

doc/source/index.rst

@@ -92,7 +92,22 @@ Juno approved specs:
 
    specs/juno/*
 
-=============
+Untargeted Specs:
+
+.. note::
+
+   The following specs are ones that have been approved but have
+   not been completed in the planned release.  Rather than leave
+   them in the originally planned release or remove them, they
+   should be made untargeted for future reference.
+
+.. toctree::
+   :glob:
+   :maxdepth: 1
+
+   specs/untargeted/*
+
+
 Volume V2 API
 =============
 
@@ -103,7 +118,6 @@ Volume V2 API
     specs/api/v2/*
 
 
-==================
 Indices and tables
 ==================