elodina/datastax-enterprise-mesos task runner

Implemented to run elodina/datastax-enterprise-mesos. Exposes stack variables:

• $app.host - elodina/datastax-enterprise-mesos scheduler address.

• $app.port - elodina/datastax-enterprise-mesos scheduler port.

• $app.api - elodina/datastax-enterprise-mesos scheduler api address in a form http://$host:$port.

• $app.cassandra-$id - cassandra node CQL endpoint in a form $host:$port

• $app.cassandra-$id.host - cassandra node host.

• $app.cassandra-$id.storagePort - cassandra node storage port.

• $app.cassandra-$id.jmxPort - cassandra node JMX port.

• $app.cassandra-$id.cqlPort - cassandra node CQL port.

• $app.cassandra-$id.thriftPort - cassandra node Thrift port.

• $app.cassandra-$id.agentPort - cassandra node Datastax agent port.

• $app.cassandraConnect - comma separated connection string for all known Cassandra nodes.

For $app == dse that has Cassandra nodes 0 and 1 variables would be:

• dse.host, dse.port and dse.api for scheduler.
• dse.cassandra-0 and dse.cassandra-1
• dse.cassandra-0.host, dse.cassandra-0.storagePort, dse.cassandra-0.jmxPort, dse.cassandra-0.cqlPort, dse.cassandra-0.thriftPort, dse.cassandra-0.agentPort, same for cassandra-1.
• dse.cassandraConnect