Ping on PBRcontrol API

[DanDayne]

Implementation of a separate resource on the API which would return data about the current state of PBRcontrol should be implemented.

Possible response codes:
<200> -> indicates that the API can respond to other requests
<404> -> indicates that the API is not running

Could be later used for reaching for data about active nodes - this feature must be delayed until Issue #6 is resolved.

[DanDayne]

Information about the ping method can be found here

TODO:

• Add device_id to the return information for better identification - first must resolve Implement device_id generator #13
• Find a way to check the status of java library - first must resolve JVM cannot be restarted #6