Upgrade Overture to build against Eclipse Oxygen

[peterwvj]

There's a need to upgrade Overture to build against the newest version of Eclipse, which at the current time of writing is Oxygen. The plan is to perform the upgrade immediately after Overture 2.5.4 is released (the release candidate has already been sent out). I tried to upgrade to Oxygen locally, and it seems to work well for the experiments that I have carried out (there are no Eclipse API changes that affect Overture). The only changes required to perform the upgrade are:

diff --git a/ide/pom.xml b/ide/pom.xml
index 39341c7f1b..55ec687a4b 100644
--- a/ide/pom.xml
+++ b/ide/pom.xml
@@ -164,9 +164,9 @@ the manifests, though.
 
   <repositories>
     <repository>
-      <id>eclipse-neon</id>
+      <id>eclipse-oxygen</id>
       <layout>p2</layout>
-      <url>http://download.eclipse.org/releases/neon</url>
+      <url>http://download.eclipse.org/releases/oxygen</url>
     </repository>
   </repositories>