Moved ZK_ROOT and ZK connection string retrieval to ZooKeeperConnector.
Minor cleanup.
Added an Instance POJO for holding instance Sling ID, config, and endpoints.
Added interfaces to be used by Orchestrator.
Added InstanceManager (to be used by Orchestrator) and a simple extension.
Broke the project down into three modules:
* common (shares common functionality of instance and orchestrator)
* minion (instance functionality)
* orchestrator (orchestrator functionality)
Added hashCode() and equals() to Instance
InstanceListeners need to implement AutoCloseable to close resources in close().
Added initial implementation of Orchestrator elements:
* Orchestrator is the main orchestrating component which interconnects an InstanceListener, an InstanceManager, and a ConfigTransitioner.
* ZooKeeperInstanceListener is an implementation of InstanceListener that listens to instance announcements on ZooKeeper.
* ModProxyConfigTransitioner is an implementation of ConfigTransitioner which reconfigures the httpd mod_proxy module to point to new instances.

Notes:
* httpd, mod_proxy, and mod_proxy_balancer must be installed (maybe some other modules as well)
* httpd.conf must "Include" a separate config file inside its <Proxy> directive. This separate config file will contain the BalancerMember list.
* To restart httpd usually a sudo password is required. It can be provided as a parameter (below), or instead the sudoers file can be edited to include the following line:
	myuser	ALL=(ALL) NOPASSWD: /usr/sbin/apachectl

System parameters:
* sling.devops.zookeeper.connString (ZK connection string; default: "localhost:2181")
* sling.devops.proxy.executable (path to httpd executable; default: "apachectl")
* sling.devops.proxy.configPath (path to the separate proxy config file mentioned above; default: "/private/etc/apache2/mod_proxy_balancer.conf")
* sling.devops.manager.n (N parameter for SimpleInstanceManager, number of instances required for a config before it can be transitioned to; default: 2)
* sudo.password (default: none)
Updated system property strings to the ones mentioned in previous commit.
InstanceManager shouldn't decide whether a config is satisfied or not, that's the Orchestrator's job.
Renamed "instance" package to "minion", moved ZooKeeperConfigAnnouncer to it too.
Renamed ConfigAnnouncer to InstanceAnnouncer.
Added a Minion component, converted InstanceAnnouncer classes to regular classes, which the Minion manipulates.
Updated readme.
Updated readme.
Merge branch 'master' of https://github.com/ArtyomStetsenko/sling-devops-vol1

Conflicts:
	README.md
Added httpd configuration to readme.