Propagate JENKINS_JAVA_HOME to Jenkins process as JAVA_HOME

This was working correctly for JBoss and Tomcat controllers, Winston controller
was affected. Effectively fixed once https://github.com/jenkinsci/lib-process-utils/pull/1
is integrated.

Using wistone controller JAVA_HOME was propagated to Jenkins and further to processes
launched form it. And since Java 8 is used on jenkins.ci.cloudbees.com to run harness,
plugins.FindbugsPluginTest.build_simple_freestyle_mavengoals_project because of
https://jira.codehaus.org/browse/MFINDBUGS-194.
Simplify JENKINS_HOME setting for Local controller
Fix NodeLabelParameterPluginTest#run_on_a_particular_offline_slave
CHANGED: refactored TaskScannerAction class to only return the requested WebElements. All assertions and further assert* methods moved to TaskScannerPluginTest.java
CHANGED: Job.getPublisher now throws a NoSuchElementException if the requested publisher is not available (open comment from PR #43)
ADDED: introduced a asTrimmedStringList method to the abstract class to support the refactoring below
CHANGED: refactored the functions to get the source file line and a certain warnings tab row in order to avoid handling of WebElement objects in the test class
ADDED: an expected XML file for tasks API and an appropriate test in TaskScannerPluginTest (equivalent to the API test in FindbugsPluginTest)
ADDED: new TaskScannerPluginTest case which deals with multiple task tags
ADDED: new TaskScannerPluginTest case which deals with fixed / closed warnings.
CHANGED: amended AbstractCodeStylePluginAction class to get contents from the "Fixed" tab and introduced a (more or less) generic function to map table cells to a map
ADDED: a variant of fileset1 which contains less open tasks
ADDED: new TaskScannerPluginTest case to check the "Run always" option
ADDED: new TaskScannerPluginTest case which checks the handling of status thresholds (w.r.t. total warning count)
ADDED: appropriate method in TaskScannerAction to retrieve the "Plug-in Result:" output
ADDED: a further file set which is necessary for the new test case
CHANGED: added a FIXME in AbstractCodeStylePluginAction as the reliability on the position of a certain warning number in the summary table is not given, i.e. the particular function may not return the desired warning number
CHANGED: did some corrections / improvements to AbstractCodeStylePluginAction and TaskScannerAction based on comments in PR #52
CHANGED: fixed expected results regarding changed warning determination
ADDED: an simple spreadsheet which has been used to develop the Task Scanner tests (especially the threshold test case)
CHANGED: selectors for methods get<PRIO>WarningNumber() amended to use IDs
CHANGED: refactored assert*Tab methods according to comment by uhafner (PR #52)
CHANGED: refactored TaskScannerPluginTest#status_thresholds to increase readability: each step is now a private method. (according to comment by uhafner, PR #52)
CHANGED: introduced a 7th step to status_thresholds test to get a stable build at the end (updated scenario spreadsheet accordingly)
CHANGED: 2 additional evaluations in test single_task_tags_and_exclusion_pattern
Revert "attempt to fix test setup bug regarding maven project builds."

This reverts commit 53422868a80a6a6f17249d3c980826057eb183e9.
Merge branch 'task_scanner_test_extension' of https://github.com/hm-ende/acceptance-test-harness into tasks

upstream into a topic branch.
Fixed imports.