TMDM-6803: "Staging Area : Progress and Stats do not reflect Match&Merge phase"

Huge refactor of the staging area controller web app (previous design unsuitable for any enhancement).
Removes unit tests (testing only XML parsing), to be rewritten.
(https://jira.talendforge.org/browse/TMDM-6803)
TMDM-7537 : Set the refresh results on , doing validaion the current validation panel shows nothing.
TMDM-6803: "Staging Area : Progress and Stats do not reflect Match&Merge phase"

Continue refactor of the staging area controller web app (previous design unsuitable for any enhancement).
Fixes remaining configuration issues.
(https://jira.talendforge.org/browse/TMDM-6803)
Merge remote-tracking branch 'origin/bugfix/TMDM-7537' into bugfix/5.6/TMDM-6803

Conflicts:
	org.talend.mdm.webapp.stagingarea/src/main/java/org/talend/mdm/webapp/stagingarea/control/shared/controller/rest/StagingRestServiceHandler.java
	org.talend.mdm.webapp.stagingarea/src/main/java/org/talend/mdm/webapp/stagingareacontrol/client/controller/CurrentValidationController.java
	org.talend.mdm.webapp.stagingarea/src/test/java/org/talend/mdm/webapp/stagingareacontrol/client/rest/ClientResourceMockWrapper.java
	org.talend.mdm.webapp.stagingarea/src/test/java/org/talend/mdm/webapp/stagingareacontrol/client/rest/StagingRestServiceHandlerGWTTest.java
	org.talend.mdm.webapp.stagingarea/src/test/java/org/talend/mdm/webapp/stagingareacontrol/client/view/ResourceMockWrapper.java
TMDM-6803: "Staging Area : Progress and Stats do not reflect Match&Merge phase"

Switch to an 'infinite' progress bar that runs until validation completes.
Fixes minor UI glitches (cancel button not in the middle).
Improves automatic autorefresh=false on close tab (hooks to the JS event on tab close).
Fix cancel wrong behavior due to missing callback for REST client.
(https://jira.talendforge.org/browse/TMDM-6803)
TMDM-6803: "Staging Area : Progress and Stats do not reflect Match&Merge phase"

Refactors concept list to:
* leverage Metadata API
* actually take into account language.
(https://jira.talendforge.org/browse/TMDM-6803)
Merge branch 'maintenance/5.6' into bugfix/5.6/TMDM-6803

Conflicts:
	org.talend.mdm.webapp.welcomeportal/src/main/java/org/talend/mdm/webapp/welcomeportal/client/rest/StatisticsRestServiceHandler.java
TMDM-6803: "Staging Area : Progress and Stats do not reflect Match&Merge phase"

Fix issue relative to wrong documentation for concept list in staging area browser (missing indication of what value is used for UI).
(https://jira.talendforge.org/browse/TMDM-6803)