People Picker support for Groups (issue #8)

- introduced new input param (type) allowing user to set type of search.
- Changed demo to set the Type = All
Updated documentation for People Picker widget to detail new input param (type)
Enhanced Filter Panel widget to support people fields that are set to only pick groups
Clarifications to the Filter panel documenation.
Bug fixes to the fillTemplate utility.
Filter panel fix to include logicalType on the returned urlParam value.
Updates to the plugin and demo showcase page to include latest changes.