Support group selection for import

When importing contact data, the user should be able to multi-select existing groups which the new contacts should be added to, and/or have the option of creating a new group from the imported set.

We may want a new separate step in the wizard for this - but for now you can toss it onto the Preview step:

[ ] Add imported contacts to existing Group(s) [v - select group - ]

[ ] Create a new Group and add imported contact to this Group

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Select group control is scrollable div of checkbox rows as in Search forms - so user can check on or several groups easily.

I think we can include CRM/Group/Form/Edit.tpl in the import preview template in a hidden block, and then If 'create new group' is checked - unhide it (display: block).