Drop back to Eclipse 2019-03 to avoid m2e regression

Closes gh-15200

CONTRIBUTING.adoc

@@ -155,9 +155,9 @@ to Maven by setting a `MAVEN_OPTS` environment variable with the value
 
 
 === Importing into Eclipse
-You can import the Spring Boot code into any Eclipse 2019-06 based distribution. The
+You can import the Spring Boot code into any Eclipse 2019-03-based distribution. The
 easiest way to setup a new environment is to use the Eclipse Installer with the provided
-`.setup` file (in the `/eclipse` folder).
+`spring-boot-project.setup` file (in the `/eclipse` folder).
 
 
 ==== Using the Eclipse Installer
@@ -168,7 +168,7 @@ provision a new environment. To use the installer:
   https://www.eclipse.org/downloads/packages/installer[Eclipse Installer].
 * Switch to "Advanced Mode" using the drop down menu on the right.
 * Select "`Eclipse IDE for Java Developers`" under "`Eclipse.org`" as the product to
-  install and click "`next`".
+  install, `2019-03` as the product version, and click "`next`".
 * For the "`Project`" click on "`+`" to add a new setup file. Select "`Github Projects`"
   and browse for `<checkout>/eclipse/spring-boot-project.setup` from your locally cloned
   copy of the source code. Click "`OK`" to add the setup file to the list.

eclipse/spring-boot-project.setup

@@ -66,10 +66,14 @@
         name="org.eclipse.jst.server_adapters.ext.feature.feature.group"/>
     <requirement
         name="org.eclipse.jst.server_ui.feature.feature.group"/>
-    <requirement
-        name="org.eclipse.wst.server_adapters.feature.feature.group"/>
     <requirement
         name="org.eclipse.jst.web_ui.feature.feature.group"/>
+    <requirement
+        name="org.eclipse.m2e.feature.feature.group" versionRange="[1.11.0, 1.12.0)"/>
+    <requirement
+        name="org.eclipse.oomph.setup.maven.feature.group" versionRange="[1.12.0, 1.13.0)"/>
+    <requirement
+        name="org.eclipse.wst.server_adapters.feature.feature.group"/>
     <requirement
         name="org.eclipse.wst.web_ui.feature.feature.group"/>
     <requirement
@@ -85,7 +89,7 @@
     <repository
         url="https://repo1.maven.org/maven2/.m2e/connectors/m2eclipse-buildhelper/0.15.0/N/0.15.0.201405280027/"/>
     <repository
-        url="https://download.springsource.com/release/TOOLS/sts4/update/e4.12/"/>
+        url="https://download.springsource.com/release/TOOLS/sts4/update/e4.11/"/>
     <description>
       Install the tools needed in the IDE to work with the
       source code for ${scope.project.label}