[BEAM-775] Remove Aggregators from internal DoFn runner-specific code

[pabloem]

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This PR depends on PR 2184 being merged first.
An important note is that it changes the signature of some DoFnRunner implementations. This should probably be reviewed by a Spark and Apex runner developers as well.

[pabloem]

r: @bjchambers

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Build result: FAILURE

[...truncated 589.80 KB...] ... 61 moreCaused by: java.io.FileNotFoundException: /home/jenkins/jenkins-slave/workspace/beam_PreCommit_Java_MavenInstall/.repository/org/apache/ant/ant/1.9.4/ant-1.9.4.jar (No such file or directory) at java.util.zip.ZipFile.open(Native Method) at java.util.zip.ZipFile.(ZipFile.java:219) at java.util.zip.ZipFile.(ZipFile.java:149) at java.util.jar.JarFile.(JarFile.java:166) at java.util.jar.JarFile.(JarFile.java:103) at sun.net.www.protocol.jar.URLJarFile.(URLJarFile.java:93) at sun.net.www.protocol.jar.URLJarFile.getJarFile(URLJarFile.java:69) at sun.net.www.protocol.jar.JarFileFactory.get(JarFileFactory.java:99) at sun.net.www.protocol.jar.JarURLConnection.connect(JarURLConnection.java:122) at org.apache.tools.ant.taskdefs.Antlib.createAntlib(Antlib.java:69) ... 62 more2017-03-09T02:10:59.095 [ERROR] 2017-03-09T02:10:59.095 [ERROR] Re-run Maven using the -X switch to enable full debug logging.2017-03-09T02:10:59.095 [ERROR] 2017-03-09T02:10:59.095 [ERROR] For more information about the errors and possible solutions, please read the following articles:2017-03-09T02:10:59.095 [ERROR] [Help 1] http://cwiki.apache.org/confluence/display/MAVEN/PluginExecutionException2017-03-09T02:10:59.095 [ERROR] 2017-03-09T02:10:59.095 [ERROR] After correcting the problems, you can resume the build with the command2017-03-09T02:10:59.095 [ERROR] mvn -rf :beam-runners-core-construction-javachannel stoppedSetting status of e7ae283 to FAILURE with url https://builds.apache.org/job/beam_PreCommit_Java_MavenInstall/8238/ and message: 'Build finished. 'Using context: Jenkins: Maven clean install
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[coveralls]

Changes Unknown when pulling 86a4692 on pabloem:remove-agg-from-runners-java into ** on apache:master**.

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[bjchambers]

Could this be split up into multiple, smaller PRs? It would enable faster review/commit cycles. It would also be help to divide them up on runner boundaries, so that it is easier for each runner team to review.

[pabloem]

Yes. I plan to split this into multiple PRs.