Use tomcat-native by default

We have made some internal benchmarks of Artifactory and tweaked the configuration to use tomcat-native with the APR Listener/Connector and we've seen a ~50%(!) increase in throughput on large file transfers. Might be worth considering making tomcat-native an explicit dependency and adding the following configuration to /var/opt/jfrog/artifactory/tomcat/conf/server.xml

<Listener className="org.apache.catalina.core.AprLifecycleListener" useAprConnector="true"/>

<Connector port="8081" sendReasonPhrase="true" relaxedPathChars='[]' relaxedQueryChars='[]' maxThreads="200" protocol="org.apache.coyote.http11.Http11AprProtocol"/>