Disable concurrent Quartz scheduling of indexing  (see #11945)

With Quartz concurrency enabled, the indexer appears to be getting stuck
in a deadlock when one or more thread experiences an OOM error. Since,
currently, only one thread can index at a time anyway this disables
concurrency in Quartz as a workaround.
Change logging in import-cli
Initial commit to replace menu by Checkbox menu.
Add option to add all the users.
Add/remove users to tree.
Allow to remove logged-in user from the display.
Enabled selection if no user displayed.
Add selection icon.
Do not allow group selection in user view.
Review the group menu in group display view.
Replace 16x16 icon by 8x8 icon.
Do not visit the browser when groups >1.
Fix selection of users in menu.
Remove the last group.
Make the group menu selectable.
Modify controls used to display groups/users menu.
Handle user in only one group.
Display data in group view when user in one group only.
Remove unused imports.
hide popup menu after selection.