OF-1347: Improve Admin Console Group Edit page (#822)

This commit adds some UX improvements to the 'edit group' page on the admin console.

src/i18n/openfire_i18n_en.properties

@@ -980,16 +980,20 @@ group.delete.delete=Delete Group
 group.edit.title=Edit Group
 group.edit.form_info=Edit group settings and add or remove group members and administrators using the \
         forms below.
+group.edit.error=Error updating group settings. Please check your error logs.
 group.edit.details_info=Edit group settings below.
 group.edit.update=Group information updated successfully.
 group.edit.update_add_user=User(s) added successfully.
 group.edit.update_del_user=User(s) deleted successfully.
 group.edit.update_user=User(s) updated successfully.
+group.edit.invalid_username=Please provide a valid username.
 group.edit.update_success=Group created successfully.
 group.edit.not_update=User(s) not added successfully.
 group.edit.share_title=Contact List (Roster) Sharing
 group.edit.share_status_disabled=Contact list group sharing is disabled
 group.edit.share_status_enabled=Contact list group sharing is enabled
+group.edit.share_with=Share group with:
+group.edit.share_group_only=Users of the same group
 group.edit.share_content=You can use the form below to automatically add this group to users' contact \
   lists. <strong>When enabled</strong>, <em>this group will only appear in the contact lists of the \
   group&#39;s members.</em>. However, you can share this group with all users or members of other groups.