update root readme, add readme in /ssn

updated info to refer to the new separate sdw-sosa-ssn repository

README.md

@@ -110,8 +110,8 @@ Each deliverable has its own folder. The issue tracker uses labels to distinguis
 
   <dt><a href="https://github.com/w3c/sdw/tree/gh-pages/ssn">ssn</a></dt>
   <dd>
-    The Semantic Sensor Network Ontology Recommendation initially developed by the Spatial Data on the Web Working Group.
-    <br/><a href="https://w3c.github.io/sdw/ssn/">Editor's Draft</a>
+    This folder is no longer used actively. It contains the state of things as they were left after SOSA/SSN was published by the Spatial Data on the Web Working Group in October 2017. Development of The Semantic Sensor Network Ontology Recommendation continues in a separate <a href="https://www.github.com/w3c/sdw-sosa-ssn">Github repository "sdw-sosa-ssn"</a>. 
+    <br/><a href="https://w3c.github.io/sdw-sosa-ssn/ssn">Editor's Draft</a>
     <br/><a href="https://www.w3.org/TR/vocab-ssn/">W3C Recommendation</a>
   </dd>
 

ssn/README.md

@@ -0,0 +1,5 @@
+# ssn - development of the SOSA/SSN ontology
+
+This folder is no longer used actively. It contains the state of things as they were left after SOSA/SSN was published by the Spatial Data on the Web Working Group in October 2017. Development of The Semantic Sensor Network Ontology Recommendation continues in a separate <a href="https://www.github.com/w3c/sdw-sosa-ssn">Github repository "sdw-sosa-ssn"</a>. 
+    <br/><a href="https://w3c.github.io/sdw-sosa-ssn/ssn">Editor's Draft</a>
+    <br/><a href="https://www.w3.org/TR/vocab-ssn/">W3C Recommendation</a>