ZEPPELIN-1816. Implement getProgress in SparkRInterpreter

[zjffdu]

What is this PR for?

Since I add jobGroup in ZEPPELIN-1769, it is easy to implement getProgress as well. It could be delegated to SparkInterpreter in the same session.

What type of PR is it?

Improvement | Feature ]

Todos

• - Task

What is the Jira issue?

• https://issues.apache.org/jira/browse/ZEPPELIN-1816

How should this be tested?

Tested manually, see screenshot

Screenshots (if appropriate)

Questions:

• Does the licenses files need update? No
• Is there breaking changes for older versions? No
• Does this needs documentation? No

[zjffdu]

@Leemoonsoo @echarles Please help review. The failed test is not relevant.

Results :
 
Failed tests: 
  ZeppelinSparkClusterTest.zRunTest:347 expected:<FINISHED> but was:<ERROR>

Caused by: org.openqa.selenium.StaleElementReferenceException: Element not found in the cache - perhaps the page has changed since it was looked up
For documentation on this error, please visit: http://seleniumhq.org/exceptions/stale_element_reference.html
Build info: version: '2.48.2', revision: '41bccdd10cf2c0560f637404c2d96164b67d9d67', time: '2015-10-09 13:08:06'
System info: host: 'testing-docker-44f30cc6-7d42-4680-bea6-3b04f484c151', ip: '172.17.0.7', os.name: 'Linux', os.arch: 'amd64', os.version: '4.8.12-040812-generic', java.version: '1.7.0_76'
Driver info: driver.version: unknown
	at <anonymous class>.fxdriver.cache.getElementAt(resource://fxdriver/modules/web-element-cache.js:9351)
	at <anonymous class>.Utils.getElementAt(file:///tmp/anonymous1954220999917500551webdriver-profile/extensions/fxdriver@googlecode.com/components/command-processor.js:8978)
	at <anonymous class>.WebElement.getElementText(file:///tmp/anonymous1954220999917500551webdriver-profile/extensions/fxdriver@googlecode.com/components/command-processor.js:11965)
	at <anonymous class>.DelayedCommand.prototype.executeInternal_/h(file:///tmp/anonymous1954220999917500551webdriver-profile/extensions/fxdriver@googlecode.com/components/command-processor.js:12534)
	at <anonymous class>.fxdriver.Timer.prototype.setTimeout/<.notify(file:///tmp/anonymous1954220999917500551webdriver-profile/extensions/fxdriver@googlecode.com/components/command-processor.js:621)
Results :
Tests in error: 
  ZeppelinIT.testAngularDisplay:157->AbstractZeppelinIT.waitForText:84 » StaleElementReference

[Leemoonsoo]

LGTM

[Leemoonsoo]

Merge to master if there're no further discussions.

[echarles]

LGTM