Reverting groups selection widget
OPAL-2252 - made sure the TabPanel.onShow() event has a target.
Merge pull request #457 from emorency/OPAL-2290-Variable-edit-validation

Reverting groups selection widget
Merge pull request #459 from kazoompa/bug-OPAL-2252

OPAL-2252 - made sure the TabPanel.onShow() event has a target.
OPAL-2283 identifiers mapping name handled when assigning in R (applies to datashield as well)
PMD fix
Enable SessionValidationScheduler