Hold active tasks in a map, but cache finished tasks briefly
Allow lookup of finished tasks; test that onComplete is called
Merge pull request #484 from zanata/optimize-copytrans

:+1: Verified
Merge pull request #507 from zanata/async-task-manager

Hold active tasks in a map, but cache finished tasks briefly
[maven-release-plugin] prepare release server-3.4.2
[maven-release-plugin] prepare for next development iteration
Make sure csrf tokens match on client and server.
Fix checkstyle violations.
Refactor some exception handling and extract a method.
Merge pull request #527 from zanata/gwt-token-mismatch

Make sure csrf tokens match on client and server.
Merge remote-tracking branch 'origin/release' into integration/master

Conflicts:
	functional-test/pom.xml
	pom.xml
	zanata-model/pom.xml
	zanata-war/pom.xml
	zanata-war/src/main/java/org/zanata/async/AsynchronousTaskExecutor.java
	zanata-war/src/main/java/org/zanata/async/TaskExecutor.java
	zanata-war/src/main/java/org/zanata/service/impl/AsyncTaskManagerServiceImpl.java
	zanata-war/src/main/resources/messages_en_GB.properties
	zanata-war/src/main/resources/messages_ja.properties
	zanata-war/src/main/resources/messages_uk.properties
	zanata-war/src/main/resources/messages_zh_TW_Hant.properties
	zanata-war/src/main/webapp/WEB-INF/pages.xml
	zanata-war/src/main/webapp/admin/processmanager.xhtml