switch to gradle

gradle files added
gradle: plugins added
build: files added
.travis.yml: gradle cache stored
distribution: tar and zip file stuff added
broker/build.gradle: osgi plugin added
build: bintray upload added
pom: files removed
distribution: assembly.xml removed
gradle: test ouput added to sub builds
.editorconfig: gradle files added
build: wrapper task added
osgi: added to h2_ and mapdb_storage
gradle: files cleaned
build.gradle: jars used for tar/zip

osgi_test/README.md

@@ -2,4 +2,4 @@
 
 to run the osgi tests use:
 
-    mvn clean && mvn install -DskipTests=true -Dmaven.javadoc.skip=true -B -V && mvn -B test -pl osgi_test
+    ./gradlew install moquette-osgi-test:test --rerun-tasks