Revert "Update project version to 2.0"

It turned out, that maintaining 1.x on a separate branch is the horror.
Now the plan is to support OSIAM < 2.3, >= 2.5 and >= 3.0 on the master
branch with a version of 1.x. This will also be done for the connector.

This reverts commit e05f43b.

Author: tkrille

pom.xml

@@ -26,7 +26,7 @@
 
     <groupId>org.osiam</groupId>
     <artifactId>scim-schema</artifactId>
-    <version>2.0-SNAPSHOT</version>
+    <version>1.6-SNAPSHOT</version>
 
     <name>scim-schema</name>
     <description>SCIM conform data types used by OSIAM services and OSIAM connector4Java for data exchange</description>