Unconfigure slf4j.simple when m2e.logback.feature is installed

Disable slf4j.simple when present during the installation of the
m2e.logback feature.
This prevents warnings about multiple slf4j providers found in the
runtime and the potential to have slf4j.simple being selected as
provider in use.

Author: HannesWell

org.eclipse.m2e.logback.feature/p2.inf

@@ -4,6 +4,11 @@ requires.0.namespace=org.eclipse.equinox.p2.iu
 requires.0.name=configure.logback.classic
 requires.0.range=[$version$,$version$]
 requires.0.greedy=true
+requires.1.namespace=org.eclipse.equinox.p2.iu
+requires.1.name=unconfigure.slf4j.simple
+requires.1.range=[$version$,$version$]
+requires.1.greedy=true
+requires.1.optional=true
 
 #Create a IU fragment named configure.logback.classic
 units.0.id=configure.logback.classic
@@ -23,3 +28,22 @@ units.0.hostRequirements.0.namespace=osgi.bundle
 units.0.hostRequirements.0.name=ch.qos.logback.classic
 units.0.hostRequirements.0.range=[1.3,1.6)
 units.0.hostRequirements.0.greedy=false
+
+#Create a IU fragment named unconfigure.slf4j.simple
+units.1.id=unconfigure.slf4j.simple
+units.1.version=$version$
+units.1.provides.0.namespace=org.eclipse.equinox.p2.iu
+units.1.provides.0.name=unconfigure.slf4j.simple
+units.1.provides.0.version=$version$
+units.1.instructions.install=org.eclipse.equinox.p2.touchpoint.eclipse.installBundle(bundle:${artifact});
+units.1.instructions.uninstall=org.eclipse.equinox.p2.touchpoint.eclipse.uninstallBundle(bundle:${artifact});
+units.1.instructions.configure= \
+  org.eclipse.equinox.p2.touchpoint.eclipse.setStartLevel(startLevel:-1); \
+  org.eclipse.equinox.p2.touchpoint.eclipse.markStarted(started:false);
+units.1.instructions.unconfigure= \
+  org.eclipse.equinox.p2.touchpoint.eclipse.setStartLevel(startLevel:2); \
+  org.eclipse.equinox.p2.touchpoint.eclipse.markStarted(started:true);
+units.1.hostRequirements.0.namespace=osgi.bundle
+units.1.hostRequirements.0.name=slf4j.simple
+units.1.hostRequirements.0.range=[2.0,3.0)
+units.1.hostRequirements.0.greedy=false