Use Tycho version 0.6.0

Changed Tycho version from 0.6.0-SNAPSHOT to 0.6.0 (i.e. release).
SNAPSHOT versions are transient and should only be used for testing
purposes only. Also removed now unnecessary <pluginRepositories/>
element from JGit parent pom.xml file.

Change-Id: Ie386b2dbcba43c1ccec10465978d12d6829c6150
Signed-off-by: Igor Fedorenko <igor@ifedorenko.com>
Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>

pom.xml

@@ -124,7 +124,7 @@
     <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
     <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
 
-    <tycho-version>0.6.0-SNAPSHOT</tycho-version>
+    <tycho-version>0.6.0</tycho-version>
   </properties>
 
   <repositories>
@@ -135,23 +135,6 @@
     </repository>
   </repositories>
 
-  <!--
-    Temporary, until we sycn Tycho to maven central,
-    see https://issues.sonatype.org/browse/TYCHO-312
-   -->
-  <pluginRepositories>
-    <pluginRepository>
-      <id>nexus</id>
-      <url>http://repository.sonatype.org/content/groups/public</url>
-      <releases>
-        <enabled>true</enabled>
-      </releases>
-      <snapshots>
-        <enabled>true</enabled>
-      </snapshots>
-    </pluginRepository>
-  </pluginRepositories>
-
   <build>
     <plugins>
       <plugin>