Add gradle-wrapper.jar and update .gitignore

Added gradle/wrapper/gradle-wrapper.jar to the repository and removed '*.jar' from .gitignore to allow jar files to be tracked. This change enables versioning of the Gradle wrapper binary.

Author: LarsEsDoch

.gitignore

@@ -11,7 +11,6 @@
 .mtj.tmp/
 
 # Package Files #
-*.jar
 *.war
 *.nar
 *.ear